Fighter subclasses:
Warrior (the Basic Fighter)
Knight
Gladiator
Duelist
Warlord
Samurai
others, such as Cavalier
Magic-User subclasses ("Mage" for short): (In this way, the various iterations of names for "wizard" are given new life: BECMI and 1e "Magic-User", the 2e "Wizard Group" and "Mage (generalist) Class", and the 3e and 4e Wizard class.)
Wizard (the Basic Mage)
Illusionist
Sorcerer
Warlock
Enchanter
Necromancer
Diviner
Transmuter
Abjurer
Evoker
Wild Mage
others, such as Wu-jen and Sha'ir
Rogue subclasses:
Thief (the Basic Rogue)
Assassin
Acrobat
Scout
Vagabond
A subclass for each Playtest scheme? Treasure Hunter? Rake? (Need to distinguish Rogue Trickster from Cleric Trickster.)
others, such as Ninja and Pirate!
Cleric subclasses: (I suggest that the Playtest deity names become the subclass names)
Lifegiver (the Basic Cleric)
Lightbringer
Protector
Trickster
Warbringer
a Cleric subclass for each major domain of spells or divine portfolio
Paladin subclasses: (The 2e Red Steel setting has a name for "specialty paladins": Defender. But that name has different connotations since the 3e Dwarven Defender and 4e Defender role. If "Defender" or "Champion" were used as the class-name, then "Paladin" could be kept as the name for the standard LG subclass)
Honorbound (the Standard LG Paladin; the name is from the "Paladin of Honor" and Mystara's "Honorbound")
Warden (=Mystara's "Druidic Knight")
Anti-Paladin (a.k.a. Blackguard)
other Variant Paladins
Ranger subclasses: A distinct name for each of the Playtest options, such as Giantslayer.
Druid subclasses: A distinct name for each of the Playtest options.
Monk subclasses:
Initiate of Mercy
Initiate of the Phoenix
Initiate of Stone's Endurance
Initiate of the Four Storms
Barbarian subclasses: ?
Bard subclasses: ?
Even though in earlier editions, some classes were subclasses of others (Paladin and Ranger were Fighter subclasses), make these ten the Standard Classes. Except for Psion, might not need to make anymore Classes.
Since other classes will have distinct names for each subclass (for example, the Fighter subclasses: Warrior, Knight, and Gladiator), how about making the existing generic deity/portfolio name from the Playtest the name of the Cleric subclass.
Cleric subclasses:
-Lifegiver (the Basic Cleric, the typical healer)
-Lightbringer
-Protector
-Trickster
-Warbringer
In this way, it will be clearer that a single deity could have Clerics from different subclasses. For example, Apollo could have Lifegivers and Lightbringers.
If more or better names are needed, appropriate specialty priest names from the Forgotten Realms might be "genericized". For example, if there were a Cleric subclass devoted to magic, the subclass could be called a "Magistrati".