i would like to see the outfits serve an actual purpose aside from just looking cool. If it's at night and I'm all in dark clothing, or camouflage, or even a Ghillie suit as mentioned and I'm trying to stealth an outpost and the cult enemy can still see me from a mile a way then what good is it?
Now of course being "invisible" in either dark or camouflage clothing would be way to over powered. So a work-around to that would be to have some of the cult members wear night vision so they could see you no matter what.
Although, I don't know if such a feature could even be added into this game.