because he doesnt like Nova. and i think it would be for the best if he doesnt show up as long Gunn directs GOTG, Because while i wont mind what he would do with him, he could kill him off or sideline to a minor character which would make fans upset, remember the Arcee thing in ROTF or the Venom thing in SM3, characters that werent liked by the director of those films?
he havent said exactly why he doesnt like him, he just doesnt. also another thing is that he wants Peter Quill to be the only earthling in the GOTG movies
He would have to return in a vision or flashback of sorts. We know what this Infinity Stone does, and it destroys things completely. There is no coming back from that. However, Red Skull can come back because we know the Tesseract transported him somewhere.
I would laugh if Kevin Bacon was cast as Star-Lord's father just because of the Footloose reference. I really wouldn't mind him returning if they could revive him in some way.
I don't know about the whole Kevin Bacon thing... meta jokes can be funny, but I think this one would take the viewer too far out of the movie. I don't think a cheap gag is worth harming the integrity of the film. It would be like the Avengers having a conversation about the real life Robert Downey Jr. and Samuel L. Jackson.
I would honestly be ok with them bringing Ronan back from the dead. I feel like you could still do a lot with him.