I'm gonna be way too busy with this game to think about the next for the foreseeable future, though I've often wanted to make something like evil islands - a russian stealth RPG where constant savescumming is like the main feature, and it had a cool crafting system I haven't really seen elsewhere.
I'm glad you're liking ufwg, I've spent a few months working on core mechanics by now, so although there isn't much content yet it's more a matter of writing new areas. Though some mechanics are still unfinished, especially greater time manipulation is gonna be hard probably.
I'm not sure about fully open sourcing it, but mostly cause code is a huge mess right now. Not sure this game makes sense for mods either, but I could share the repo with you when it's a bit cleaned up in a month to poke around.
I'm also curious about your thoughts on terraformental. You can email dk1a@protonmail.com btw