How should they handle Wolverine in this movie? (if he had to be in it..)
Assuming that DoFP establishes two timelines (the original movies and First Class), would you rather see:
A: Wolverine the time-traveller from the original movies.
B: Wolverine from the First Class timeline.
C: No Wolverine
I think "A" and "C" are most appealing. Personally I don't think he should be in it (as he's been the star of 4, soon to be 5, films).
If he had to be in it, I'd prefer "A" over "B". For "B", a rookie Wolverine joining the team again would be a repeat of X1 (but weirder/awkward, especially if young Scott, young Jean are in it (perhaps born earlier due to time-travel butterfly effect or something. We did see Scott/Storm 'cameos' in FC afterall)
I think Wolverine the time-traveller might be more interesting. (Wolverine is a great candidate for the time-traveller, as he would able to live long enough to see the changes he possibly makes).
They could have him trying to right certain wrongs he made (in the original trilogy) regarding the giant threat that destroys the original timeline's future but also his personal decisions. Perhaps he'll be the responsible one, mentoring the hothead teen recruits. Perhaps he'll be the one resistant against Xavier recruiting Jean. Perhaps he'll try to put his other self on a different path.
Two Wolverine's might be complicated though; maybe they'll just keep it simple by having him mind-time-travel instead (occupying his First-Class timeline's body).