They're all interesting ideas. The Second and Third sound the easiest to achieve within the scope of the game, so it'd just be a matter of balance and tradeoffs.
For weapons, it's the usual stats to balance.
Shields factor in cargo space/max capacity/regen rate/offline (rebuild) time/rebuild power draw. There's apparently a variable called "Constant Power Draw" that sounds pretty interesting. From the sound of it, you could set it to any value under the ship's powercore regen and effectively reduce this regen rate (similar to the technerf)...or even go over it and make it a race to do DPS, though that'd be a bit weird (it would make docking modules in carriers important as "recharge stations"). This means the most powerful shields will come at the cost of offensive capacity, which arguably sounds like a better tradeoff than just cargo space->hull increase.
I'd be more inclined to have these shields be a "sidegrade" that do unique things and are well balanced to standard shields rather than an extreme raw "upgrade" that gives everyone with the credits a massive advantage.
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