the hulk really has pretty poor rogue's list, even the abomination is a poor villain that is pretty much a straight up anti hulk.
I dont know why people want villains when a whole film could be held by simply the hulk battling himself. All that is required is the introduction of doc samson.
imagine either a psychological or physical separation of bruce and the hulk that awakens a third party, the grey hulk, which is bruce's deep desires and self vanity that thinks he should rule the planet, the rest of the film can be based on samson and rick attempting to subdue the grey hulk so that a re-merger can happen before bruce either is lost or dies.
THAT could easily carry a great film without any outside villainy intervention. The subject was touched in the 90s cartoon and it worked really well there.
heck with potential cross overs, imagine bruce going up against the hulk in some sort of hulkbuster costume.
tie in an avengers team up to stop a grey hulk and you have one truelly awesome film concept without the need for the hulk's sucky lineup.
you could even throw in she hulk in there...
personally i think that is room for two films no probs.
I don't know why everyone wants to see big villain tussles all the time, let's for once have a film that centralises on one character and their growth or demise without an outside antagonist, it'd be such a change to the rest of the superhero films outther and i think it could really work on not only a deep and intellectual level but also on an entertaining one as well.
What better to have potentially (to the outside world) the most 2d character completely fleshed out into a 3d real world and have films dedicated to giving this character complete and utter depth so someone can come out of the series knowing as much about hulk persona as a long term fan.