Just acknowledging the fact that a PH film doesn't sound like the smartest move on paper.. GOTG didn't either and it turned out to be great but that doesn't automatically sign me up for the rest of Marvel's future flicks.
Biggest question i have about it is how does it advance their overall story. Seems like they're entering a point where every standalone has major significance in expanding the overarching plot and i personally don't know how Planet Hulk will do that.
I imagine a situation where he's sent off somewhere and they use this as a way to crossover some of the cosmic stuff with what's going on here. Could be something with the inhumans, or he crosses path with the Guardians... hell i could even see something where he's sent to Asgard and they make a Hulk/Thor buddy film
Don't have the slightest idea but i'm interested in seeing where they take this.