Is it too late for me to say I'm with DaEezT? I actually like the idea of armor mods, but somehow armor weight feels off. Kinda like... overthinking it a bit. Any changes to the armor system (or anything, really) should focus on conferring new abilities rather than adding for drawbacks for Instant Tactical Depth. (Just add water!)
Basically, I'm with you Kornel, in that another layer or two of options wouldn't hurt. However I think the best way to do that is to make the player choose a set of equipment and perks crafted to their play style, and influenced to a large degree by luck. So, more weird equipment, a deeper perk tree with more branches, stuff like that. DoomRL should be a playground, not a chessboard. Nobody works out a cost-benefit analysis of slides versus swings. They're both fun, and if you don't have time for both, you pick whichever one you like better and doesn't have somebody else on it.
PS: Since I may have rambled a bit too much in this post, here's my point. Among other problems, having any kind of system which would encourage you to take armor on and off for whatever reason is too much detail. When I have my Super Awesome Supercolliding Supersuit on, I want to keep it on and not have to worry about whether I have a 5% chance of getting macked in the face.