I have na idea that devs should give the players thay graphic tools to make players able to create new weapon,mob and gear models, also new maps etc. ,but ONLY the graphical part of it (just to be clear i don't whant them to give players chance to ingerate in game itself, it could be a disaster :< ).
They also may attach SK to the Steam Workshop system, and made such system on their own, for players who aren't playing trough Steam(btw thera are more of non-Steam players than Steam players), i know that there may be LOTS OF nonsens stupid jokes, trols etc. but i noticed that Steam Workshops comunity isn'tgiving chances for such things to be popular (shortly they ignoring them), and even if something like that became popular, it is up to devs to add or not add it to game, soi think it could be really goo idea.
Spiral Spy, Pothoshop and any modeling software. We don't need official tools to create art,