I mixed up the games in my head for a second and forgot what I was answering...
Well, the obvious solution would be to continue remaking Spore? But we're against obvious answers. Where would I go from here? I'd probably move towards the vampire survivor genre, but also towards adapting to the environment and so on. Almost everything you need is already there, you just need to add bonuses for reaching a new level and strengthening the "enemies" and the biosphere over time