The next location I add may well be a denser forest in the mountains - I'm picturing tunnels, fog, and snow at higher elevations.

I don't plan to sell it, but you can follow my twitter for updates. I'd like to keep it freely available if I can :)

https://twitter.com/anslogen

Why not both? Have a free version and a paid version with more features/terrains/cars etc.

Made a KoFi contribution. Perhaps one of your "goals" can be to hit a level where you can keep it freely available?

Much appreciated! There isn't any reason it can't be freely available; it costs almost nothing to host. Development time is the true cost, so it's more a question of how much I'm able to add.