The problem I have is that I made an attempt to make armour available to arcane magic users with a fatigue (hp) cost - however I think that by linking this to STR I had the unintended effect of penalizing all characters with low STR, and most of all the rogue and hunter classes. So much for elegance. Simply adjusting the MinSTR requirements down would just lower the cost for mages while leaving characters with a low STR in the lurch for DEX. That's not going to work, so I think a simple hp penalty based on the ac bonus is the way to go here. As for the DEX penalty - it's currently too harsh and I think that anything below scale mail should probably not even have a penalty.
After I brought this up with some options to fix it, Mike (from the comments section) brought up a really good solution to this:
What about simplifying armor in the same way you did with weapon damage? Light, Medium and Heavy. As with weapons, the actual form is as much description as anything else.I like it this idea a lot, but I do worry about two things. Firstly, I'm not sure anymore that a high STR score should relieve the DEX penalty for heavy armours. It's not like being really strong is going to let you play a lute with your gauntlets on right? Secondly I like having one armour type for each AC bonus - it gives folks something to work towards at lower levels. All that expensive armour also fits nicely with the repair bills that come from the critical hit table. But I have to admit that it is a really elegant idea. It fits.
Light has no strength restrictions but only offers +2 AC (padded, leathers etc)Medium has a 10 strength restriction and offers +4 AC (chain and the like)Heavy has a 14 strength restriction and offers +6 AC (plate, scale and so forth)The spell hit-point modifier would be, as you suggested, same as the AC bonus.
I'm going to think about it.