Lots of interesting discussion here. I wish I'd found out about the kickstarter before it closed
Chucking 2p worth in:
I like the idea of having multiple sets of armour to change depending on circumstance... BUT it should be implemented realistically. Putting on a plate mail suit takes lots of time so you couldn't change on a whim. How about being able to set up a camp for your party where you sleep/change/repair/make arrows/etc. Obviously your char would start out with 1 set of basic armour (if that) and go on to build up a stock of items. Carrying them is the challenge here maybe ponies/horses to carry extra weight
Camps might also be interesting in terms of being attacked while sleeping. No-one would sleep in a full plate set (ouch!) but might choose to sleep in a chain vest. being surprised in the night would mean you were not wearing your full plate +20 and so be more vulnerable. Also leaving gear in a camp might lead to being robbed by bandits... having a ranger or mage to track down the hideout and exact revenge becomes useful.
Two other things, I really like the idea of customising your own gear to some extent - archers make their own arrows and get better as they practice, you repair tears in hide/cloth fabric yourself. But once you get to chain/plate you need to go to a blacksmith (cheap not very good) or armourer (expensive excellent work) for repairs.
Lastly, I don't know if anyone has mentioned this but PLEASE put some serious thoughts into helmets. Full face helmets restrict vision, open helmets offer less protection. The one thing that bugged me most about BG was the helmets protect against critical hits thing. Being hit on your head, whether you are wearing a helmet or not, is going to seriously damage you and your ability to fight!