(Edit: to be clear, changed up appearance only - not any unique stats or anything - Savini Jason wasn't supposed to be more than a skin to begin with). Kickstarter backers bought him sight unseen - they just bought a unique Jason skin. His look wasn't revealed until after the fact. So no one can say "I only bought it for that specific look to be exclusive". This is really the only solution left that has a decent chance of pleasing most people. It might be easy to think that MS is going to take these away, but considering how it's been done, I have severe doubts it technically can be undone.
That is not to mention this fucking game is already a huge sore on their ass to begin with in terms of pissed off customers, I just don't think they are going to stir that pot further than GUN has already forced on them.