There are actually 'post-it' notes that have one side that is entirely adhesive so one could trim the adhesive notes to the shape of the stickers, then stick-on, stick off. Not perfect but you also cut a tab that sticks out from the stickers to facilitate unsticking. (I'm also thinking about this for SeaFall.)
Odds are we could probably use sheets of removable sticker paper (like post-it note adhesive) which would possibly eliminate the need to put the stickers on sleeves if you want to reset. Sure, you'd need to go through the decks and peel off a few dozen stickers but sleeving hundreds of cards is way more tedious.