>>8754263Really the latter relies on the former. If the final piece assortment is anywhere near similar, the alt build can't be stopped. It'll just be unofficial. The best LEGO can do to stop them is not doing the stickers that relate specifically to the alt build. However, that's an easy work around for anybody that wants it enough, which isn't hard to find in the Sonic community.
Honestly, though, LEGO might like the idea of getting away with producing one Ideas set that can be sold twice over with only needing to provide a few extra stickers. I'm would not be surprised if that's one of the reasons it got picked up.