Backer-exclusive things in general along these lines seem more of a risk than a boon---just about every time an instance of it has arisen in a Kickstarter it has been quickly, often loudly, walked right on back. What people want in general amounts to early access, quite a number want spiffy physical copies regardless of how damning the international shipping situation is becoming in general, and general game-affecting inclusions/namedrops/dev chats/etc. I really hope they've done due diligence this time around on the various successful Kickstarter RPG projects and can make it happen.