Holtzman Shield
Dune has energy shields that only allow slow objects to penetrate them. Excellent for protecting against bullets. Fading suns also has this. It's a way to make melee dueling possible in the age of guns
Guidelines and ideas
Shields have a minimum damage threshold. anything over this gets blocked
Shields could block "fast" objects. This means pretty much all missile weapons, and most melee strikes
One could combine the speed with the minimum damage
environmental damage like falls gets done just like the hits. Mythras rules already provide for being hit in multiple locations
Shields should have a maximum energy threshold before they burn out. This should be per cycle
treat Holtzman Shields like regular shields for the purposes of knockback/bashing. Thus, they can be used to push back troops
in fact, you can "attack with the shield" and it doesn't take a hand. Treat as unarmed, and as part of the style.
The Slow Blade Penetrates the Shield
So how is this emulated? I think probably as a special effect. The combat with the shields makes regular blows largely about positioning and putting your opponent at a disadvantage. Lets go with "minimize damage" being a special effect here, and a Critical one. This will let you get through the shield