First of all i'll start with the models that already are on the serv, but are t-posed:
models/stalkertnb/beri_seva.mdl - medic uaf
models/stalkertnb/cs4_wolves.mdl - heavy uaf
models/stalkertnb/beri_tyson.mdl - bare head uaf
models/stalkertnb/sunrise_cadpat2.mdl - commando uaf
models/stalkertnb/skat_cadpat.mdl - special ops uaf
models/stalkertnb/skat_free.mdl - pilot uaf
models/stalkertnb/beri_mili_officer.mdl - officer uaf

Weapon packs, that i found (may be just props so i need opinion about those):
http://steamcommunity.com/sharedfiles/filedetails/?id=559186409
http://steamcommunity.com/sharedfiles/filedetails/?id=105296204&searchtext=weapon+pack
http://steamcommunity.com/sharedfiles/filedetails/?id=352872432

Idea about mutants:
How about making a char that is a big scary mutant walking in the labs while people are doing quests there? That mutant could be in god mode and could just walk around and scare people with weird sounds, sometimes killing one of the wanderers and making rp with a ragdoll body or something like that. Here is a model of William Birkin, a known mutant monster from Resident Evil 2, that we can use for that idea:
http://steamcommunity.com/sharedfiles/filedetails/?id=137335836&searchtext=resident+evil

Also it may look a bit weird, but i found some good looking models for the millitary, also from the Resident Evil game:
http://steamcommunity.com/sharedfiles/filedetails/?id=244231325&searchtext=BSAA