I've been unsure of what to do with evil areas. Compared to vanilla DF they're actually kinda boring and quite a bit safer. Obviously, this can't stand. One of the things I've been considering is adding a new weather effect - radioactive clouds, in order to add some use for rad suits. (This might actually be a good use for the dust contamination bug, too, and it would force some inventive architcture to make use of overland crops. Of course, if they're left as they are, it might spiral out of control, so there should be some point at which they evaporate using SPEC_HEAT. Might need some help to get good values for this. As everyone who has tried to mass produce fuel rods in the older versions would know, radiation poisoning is no laughing matter.)
The other thing to add would be new creatures and this is where I'm drawing the biggest blank. I've wrung dry pretty much every old Necromunda supplement both official and fanmade and I don't really know what else to add in terms of creatures. Ghouls are one thing I've been considering, which might be useful as another creature for Scavvies (although they're still a bit OP compared to other siegers, at the moment in spite of their crappy gear and physical weakness, since they're the only ones who get building destroyers to come along on their sieges. So, anyone who has some creature ideas, especially for evil areas, please speak up.