If Jon Snow come back to life as a puppet of some other person (Melisandre or the White Walkers or Bran or whomever), it would be the least GoT thing ever.
The great thing about this show is that it defies the long held conventions of television drama.
Bringing back the character just so the actor can stay on the show would be a terrible thing to do. I, for one, hope that GRRM sticks to his book writing principles and gives no fecks about the popularity of Kit Harrington.
I'm not sure if it's such a great thing if it happens for sake of it rather than in a well thought out way. When Ned lost his head in season one, it was both shocking and truely important for the progression of the story. It added so much development to characters around him, it kicked off the different storylines of his children and changed the tone in King's Landing, especially developed Joffrey's character and the difficult relationship between him and his mother.
Ever since the big shock moments became more and more meaningless for the overall story. Most of the time they just kill off a character whose story ran into nowhere or just flat out end a storyline without any conclusion. Most of the conventions in writing and television drama actually exist for a reason and if you start killing well developed characters for the sake of it without replacing them with equally important and interesting characters, you just lose quality and it's poor writing. Even the red wedding is somewhat guilty of that, because the Bolton storyline is so poorly developed and told that at least for me it still leaves a sour taste. Yes, the moment was great and surprising and shocking. But that's it, a quick fix with no substance to it and the trade off with what we got instead wasn't worth it. It was entirely different with Ned's death in season one.
Even the minor shock moments seem much more meaningless in latter seasons than in previous ones, an obvious example would be Bran's injuries compared to Arya losing her sight. The former was a fascinating moment, an interesting piece of storytelling with a big impact to many different characters and the story. Arya going blind just seems shocking for the sake of it and has no connection to anything else.
Whatever happens to Jon or follows Jon's death better be worth it, because it really can break the show, turn it into a silly soap opera for good or actually get back on track with a fascinating story, that temporarily lost its way with many silly sideplots. At the moment, I really can't see the latter happening, because the overall writing in almost all plots has become really poor.