i'm really hoping the original storyline is done justice.
surely it won't be followed panel by panel, but to get the main ideas down is key.
this movie would have been great as the third installment in the first class series. The second film could have been used to introduce/reintroduce key characters: the sentinels, the brotherhood, wolverine (preferably not played by jackman who has ruined it, imo), mystique, etc.
the mind time traveler of course doesn't have to be kitty, as the x-men animated series so expertly showed us. but a newbie x-man would be preferable.