I probably add "save" functionality for current run in case the player is in hub. I don't intend to add "game over" state though. Things that will persist are the already mentioned sandbox map with currency for it, some kind of achievement system and anything else that I think makes sense. These things are similar to tutorial when it comes to implementing it now: it will cost me too much time and effort to maintain them while I'm still creating an actual gameplay loop. So the best thing in my opinion is to ask for patience while I'm searching for ideas that I want to lock in.