Bella might be annoyed or offended if Jacob tries to do anything with Renesmee, but if they both fall in blind love then nothing can stop ;) I am sure later Bella and Edward will allow. ^^
It's true that theres a possibility that Edward and Bella wouldn't allow it and Bella did react badly. But then again you never now Jake could probably be like "You're happy Bells. Why can't i be happy too?" and well i think the feelings are mutural between him and Nessie in a way. She had plenty of images of Bella and Jake in her mind. So i am pretty sure that if she really wanted Jake her parents would be alright with it. I mean who else could be as overprotective as Jake? i mean c'mon, Rosealie ain't got nothing on him XP
So..... yea i think that it would be alright....
I think jacob will be like a uncle to nessie. I dont think it could go any further than that. Jacob loves bella and always will deep down and to get with bellas daughter would be creepy and i dont think he could ever see nessie in that way. I hope they dont get married because that would be quite weird.