While you can use pretty much any party members that you want, there are some of them that provided very good support to this build. I will list the build that i used with them on this page. I still focused on a few of them however and you shouldn't have to use any other one for combat, as T3-M4 and HK-47 purpose doesn't involve combat, you can simply switch them as soon as you're done using the party selection screen from the Map menu.
The only skill really needed for party members to minimize gear switch is to have a high Demolition skill to recover mines. Main Character already covers Repair for part cost and T3-M4 can supply more Computer Spikes than we end up needing.
Personnal party members progression:
Carth -> Carth/Mission -> Carth/Zaalbar -> Carth/Bastila -> Carth/Canderous
Canderous/Mission, Bastila/Canderous for the Ruins
Canderous/Mission, Jolee/Mission
Jolee/Mission
Juhani/Jolee, can still keep going with Jolee/Mission until the end if you want.
Jolee is a total beast from the moment you get him. If you did complete a few side quest for credits before going to Kashyyk, he will be over level 12 already, giving him anything you need for crowd control. I used a dueling melee setup with him, but you could also use an Heavy Weapon build using a Baragwin Assault Gun or Baragwin Heavy Repeating Blaster. With his lower HP and first 2 feats already into Dueling, i prefered using the lightsaber approach for better durability as his primary role is to use powers to debilitate so we can perform constant sneak attacks.
Script: Jedi Support (only one, rest are all Default)
Attributes on level up: All Wisdom
Skill: All into Demolition as we want to minimize gear switch if not having Mission with us.
Feats (4 by level 20): Master Dueling (1), Master Flurry (3). If going with the Heavy Weapon Route, go with Weapon Profiency: Heavy Weapons (1), Light Armor (1) and Improved Rapid Shot (2).
Powers by priority (17): Insanity (3), Kill (3), Destroy Droids (1), Force Breach (2), Master Valor (2), Master Speed (3), Death Field (2), Force Resistance (1).
Gear:
Weapon: Single Lightsaber with Mantle of Force, Crystal Solari with Sigil or Upari. Can also use a crystal Rubat with Mantle of Force if you want him to have some additionnal force regeneration and less melee damage.
Armor: Demolition Sensor/Heavy Targetting Optics if going Heavy Weapons, Advanced Stabilizer Gloves/Verpine Bond Gauntlets , Dark Jedi Master Robe (looks great and pretty Skywalker like), Nerve Amplifier Belt.
Mission is amazing if used well. She has amazing defense and is the best tank for most of the game on Impossible due to that but lack a bit of damage at the start, which i why i prefer using Zaalbar to end fights faster at that point on Taris. She can also take care of any skill checks that you'll need as the cherry on top. She pairs super well with this build and Jolee with their permanent debilitation, which makes her deal sneak attacks constantly and we want to abuse that for insane damage (9-54 extra damage per attacks). The build that i chose is a two weapon fighting melee build to maximize damage as her defense is already very good. You could always go with dual blaster using Cassus Fett pistol and Saul's Sith Assassin Pistols to make her deal sneak attacks from a distance and use Calo Nord Mandalorian Heavy Pistols until then but her base damage will end up lower and she'll be at greater risk against melee foes that gets to her. You could also go with heavy weapons but there are two way better candidates for this (Juhani and Jolee).
Attributes: All strength (go all dexterity for blasters)
Skill: All class skills maxed at least until 20, then max computer use (will be much lower as a non-class skill). Rest into Treat Injury or Repair, your choice.
Feats (6): Master Two Weapon Fighting (3), Master Flurry (3), go with Master Rapid Shot instead if going with the dual pistols.
Gear:
Weapon: Echani Ritual Brand -> Ajunta Pal's Blade-> Can choose to stay with the same blade or switch to Bacca's Sword/Naga Shadow's Poison Blade, if this wasn't used in our build 2x Baragwin Assault Blade would have been optimal.
Armor: Bothan Sensory Unit, Nerve Amplifer Belt, GenoHaradan Power Gloves, Light Exoskeleton.
Juhani is pretty average once you get her and can get very powerful with lightsabers. She however has the potential to be the best ranged character in the game by far with some insane firepower, which in my opinion makes her even better. With the addition of force powers, she can also buff herself to be very resilient while debuffing strong foes into nothing. She's so fun to use that i just can't not have her once i can unlock her potential. She can use this setup to be your saver on the Leviathan.
Attribute: All dexterity
Skill: Automatic (awareness and threat injury)
Feats (6): Weapon Profiency: Heavy Weapon (1), Master Rapid Shot (3), Implant 2 (2).
Powers by priority (14) : Heal (2) Master Speed (2), Plague (2), Force Breach (2), Force immunity (2), Death Field (2), up to you for the last 2 (force armor can be used for a very long time without having to re-cast using the loading screen exploit, Improved Energy resistance can be used if you don't want Force Armor and have energy resistance for the small Leviathan part).
Gear:
Weapon: Baragwin Assault Gun -> Baragwin Heavy Repeating Blaster.
Armor: Heavy Targetting Optics (Korriban Czerka shop), Jedi Master Robe -> Star Forge Robe, Advanced Stabilizer Gloves, Nerve Amplifier Belt/Baragwin Stealth Unit/Adrenaline Stimulator, Retinal Combat Implant/Nerve Enhancement System.
The best of the tier 2 for sure but lack a little something for tier 1. Sadly on Impossible Difficulty, being tanky doesn't do it and Canderous, just like the rest of the party members, lack defense to consistently avoid damage. He can still be used for the whole playthrough and you can spend his points into demolition if you want and he will perform very well. The lack of 2x Baragwin Assault blade is going to hurt the endgame however so he's not the best for this build (amazing with Master Critical Strike, try it one time!).
Attribute: All Strength
Skills: All Treat Injury (automatic) or Demolition (many other party members can take care of that however, he does need self recovery some time)
Feats (13): Master Two Weapon Fighting (3): Weapon Specialization Melee Weapon (2), Master Toughness (2), Master Flurry (3) or Master Critical Strike (3), Master Conditionning (3) or Implant 3 (3).
Gear:
Weapon: Vibro Double Blade -> Krath Double Sword -> Bacca's Ceremonial Blade or Echani Foil/Sanasiki's Blade ( if you want to spend 7k credits) or Echani Vibroblade or Naga Shadow Poison Blade. Ajunta Pal's blade is also a solid choice.
Armor: Calo Nord's Armor, CNS Strength Enhancer, Genoharadan Power Gloves, Advanced Bio-Stabilizer Mask/Medical Interface Visor/Stabilizer Mask, Sith Regenerator/Cardio Power System if using Implants (+3 saves with Conditionning instead).
MVP of Taris for sure but lose effectiveness the further you progress. Can still be a very good jack of all trade and this build will provide the support that you want no matter your chosen setup. You could always switch from Blasters to Melee if you want and he will perform really well too, while always being inferior to Canderous in that aspect.
Attribute: 1 into intelligence, rest into dexterity
Skills: Max demolition once you get the intelligence point at level 8 then Treat Injury. He will save you from switching gear on the Leviathan.
Feats (14): Master Power Blast (2), Master Two Weapon Fighting (1), Master Toughness (3), Implant 2 or 3 (3), Master Rapid Shot (3), Master Conditionning (3) or Weapon Specialization: Heavy Weapon (2).
Gear:
Weapon: Carth Blaster/Bendak Blaster -> Dual Mandalorian Heavy Pistol -> Baragwin Assault Gun -> Baragwin Heavy Repeating Blaster if you want to keep using him. You could always stay with 2 pistols using Saul's Sith Assassin Pistol and Cassus Fett's pistol.
Armor: Military Suit -> Davik's War Suit -> GenoHaradan Mesh Armor, Advanced Stabilizer Gloves, Nerve Amplifer Belt, Bothan Sensory Unit or Heavy Targetting Optics, Advanced Combat Implant or Retinal Combat Implant.
Stays on the ship at all time with this build personnally as there is always someone who can do the job better. She's still decent however, you can have her with you at all time if you want but the fact that she's not even there for the endgame portion makes spending too much efforts on her not worth it. Here is a decent build to have an easy time on the Leviathan:
Attribute: All Dexterity
Skills: Automatic (Awareness and Treat Injury)
Feats (assuming you get her to 17, 4): Master Two Weapon Fighting (2), Master Flurry (2)
Powers (also at level 17, 14): Cure (1), Destroy Droids (3), Master Speed (3), Master Valor (3), Plague (3), Force Resistance (1) or Adv Throw Lightsaber (1). Can also use Stasis Field or Force Wave instead of Plague if you want.
Borderline usable honestly, but really lack the defense and staying power that others have. He still perform very well on areas where there are no physical damage at all as Improved Energy Resistance stacked with his Improved Toughness and Wookie Toughness will make him ignore most damage even on the star forge. He's still very vulnerable to force powers no matter what however.
Attribute: All Strength
Skill: Max Demolition, Max Treat Injury, rest into computer use or whatever you want.
Feats (8): Master Two Weapon Fighting (3). Master Flurry (2), Master Toughness (3)
Gear: Same as Canderous without Armor and Headgear.
While i love his interactions, he lacks the feats to be better in combat and the Droid parts aren't very good in Kotor1 compared to 2. He can still achieve ridiculous defense but unless you like messing with the Special droid Weapons or the Baragwin unlimited droid weapons, i wouldn't waste much time using him in combat and would simply use him for the Sand People translations and his personnal repair checks.
Attributes: All dexterity, can put a few points into constitution if you want.
Skills: Max Repair and Demolition
Feats (4): Master Rapid Shot, Toughness
Gear:
Weapon: Chuundar's Bowcaster, Baragwin Assault Gun, Baragwin Heavy Repeating Blaster.
Armor: Composite Heavy Plating, Baragwin Droid Shield, whatever you want for the rest, it really doesn't change much.
I switch him as soon as he unlocks the door to the sith base on Taris, then i use him to get Computer Spikes on the ship. Nothing near what he is in Kotor 2. He's pretty useless compared to the rest of the companions honestly but with a build this strong, why not be a real OG jedi with his protocol droid following him everywhere?
Attributes: Dexterity
Skills: Automatic (max everything)
Feats (5): Improved Two Weapon Fighting (2), Master Toughness (3).
Gear:
Weapons: Best pistols you can find so same as previously stated, Baragwin Flame Thrower.
Armor: Composite Heavy Plating, Baragwin Droid Shield, Superior Targeting Computer.