Gambit is something that more people probably would have kept playing for fun if it never had the circular firing squad matchmaking applied to it, very hard at some points. No matter what happens to gambit the drifter must stay. But there's definitely a lot of ways a new gambit could be worked into the story similar to what happened with Shaxx. People really don't like the invasions but there should be some role for guardians outside of just killing enemies and something mechanic focused that's not too complex like what's in onslaught might help freshen things up. Other than that the mode really needs a complete overhaul because more than anything it feels old a lot of the time what with the same maps in rotation and not many other changes. Then there's also the thing where what the general population enjoys tends to be somewhat different from what more traditional players like in terms of rewards relative to ability. That would no doubt be fun to figure out.