Setting idea: what if the adventure mode took place in the same world but at a different time period? I was thinking some time in the past. To me, the ruins layer in VS has felt a bit empty. I know some of them have to do with story, but what about the rest of the smaller ones? It's clear that there was once a living and dynamic world previously, and maybe Adventure mode can help fill that out.
That still leaves plenty of creative room to expand with various fantasy races, locations, mechanics, etc that is very different from the current time period but also the opportunity to tie some world-building back to the base game. It also has the advantage of being able to pass work such as concepts and assets on to other game modes. Maybe there used to be a dragon-like creature? You can find it's bones. A small village has a master smith for weapon upgrades? You can find a masterwork weapon in the ruins. You interact with an elf-like race who lives in the jungle? You can find their ruins (and stuff) in jungle biomes.
I like the idea of being able to explore an active and vibrant world in one mode, while giving context to lore in a later time period.
