I know that the game is meant to be promoting teamplay but just had this idea and I think It would be quite good.
Basically If we could have skins for Jack Carver / Jason Brody/ Citra/ The Jackal / Four Player Co-op characters / Vaas / Dr.Earheart and the standard skins of enemies in FC3 then you are practically on your way to having a free for all with multi-skin support.
Last man standing Mode and Deathmatch Mode basically
Quite an easy mode every man for himself... It's all about the skins in this mode - Lose the tattoos for this it's jump in and jump out gameplay
Personally I'll be running around as doctor earheart syringing people in the back and blowing them away with a shotgun
Somehow I see Vass with a butterfly knife
And personally thinking about it if vehicles could be included this is the best place for them in free for all