Being able to fully customize armor and weapons would be amazing.. You should be able to paint your weapons and armor (and be able to dye your clothes perhaps), be able to cut your shotguns in half to turn them into a sawed-off shotguns, shortening or lengthening your rifle, smg and pistol barrels, modify your weapon to fire higher or lower caliber ammo, even be able to engrave your weapons.. (At least some weapons, like revolvers) And perhaps with high enough tech skill, even being able to upgrade/enhance inner mechanisms of the weapon as well.... In order to get faster rate of fire, be able to change between semi-auto and full-auto and stuff like that, as far as i know no other game has done that before.. (For instance, you can take a regular Colt 1911 and turn it into burst-fire or full-auto..)
I love it how even the smallest modifications can change the appearance of a weapon drastically:
AK-47:
Beretta:
I love it how even the smallest modifications can change the appearance of a weapon drastically:
AK-47:
Beretta: