Damn, for some reason only part of my post was saved.
To sum up the first half briefly: I dislike the "+1" system since it felt arbitrary. Having a more nuanced material system and various sub-categories therein makes a lot more sense. So, for example, you have deer hide, bear hide, dire wolf hide etc. Each hide type is different in some way - you could have some that are slightly heavier, others that are more pliant, and so on. Armor should also be modifable - if I want to add a light sheet of chain links beneath my hide, I should be able to do that with the requisite skill or at the appropriate shop. That would make the hide sturider and have a better AC without jumping completely up to the next tier of armor, only sacrificing some of the beneifts of light armor in the process. There should also be a socketing/enchating system. Gems were largely useles in a lot of the old IE games. It would be cool if socketed armor utilized gems in interesting ways, or if armor could be enhance through magic. That way, light armor could be greatly improved over time but the character could still maintain the desired aesthetic appearance and still have an armor type appropriate to his abilities and strengths. It's easy to let armor get ridiculously amped up with this kind of system, so some kind of strict enchantment cap, or a system wherein enchantments are temporary or socketed gems are breakable, would be a possible solution.
Heavier armor should negatively effect movement speed, agility, and sneaking/pickpocketing/back stabbing. Having a thief skulking around in heavy plate makes no sense. The benefits of light armor need to be tangible, however. You should be proportionally more likely to avoid being hit when wearing light armor as you would be able to absorb a hit in heavy armor. In heavy armor, you get hit more often but take less damage. In light armor, hits hurt a lot more but you're able to dodge out of the way more often and flee from immediate danger more easily. It would make sense for thieves, archers, and non-fighter mages to be in lighter armor so they could do their thing (sneaking around, running around and peppering enemies with arrows/spells etc.) much more easily. This, along with my thoughts on armor materials, also speaks to the issue of the "mid-level armor" conundrum. A ranger wouldn't have to give up his ultra-light hides that don't protect at all against the attacks of upper-level creatures in favor of cumbersome heavy armor, because he could improve his hides with metals, gems, charms, etc, or even take the hides of the increasingly powerful creatures he encounters to make better and better hide armor.
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