Actually, judging by what I saw in the internet (and in real life, but I'll get to it a bit later), I actually can imagine snowmobiles in Africa, on the dirt, on concrete - basically anywhere, even without those wheels fitted to the front. The sand is definitely not a problem for these guys. And speaking of real life: living out of town, years ago we actually had a guy who had a snowmobile, and he used to drive it from... say, village to village, even on concrete. It wasn't that maneuvrable, yes, but it could take turns, well... probably much better than you think it would. That dude, he just added a homemade replaceable rub bar under the skis so he won't damage them. Theoretically, on class can have snowmobiles both with wheels and with skis, and it would reflect their stats and terrain handling.
Speaking of it, I'm actually against snowmobiles anywhere out of snow, but tracked vehicles could be added to any classes. Patriot Compadre can fit among the Monster Trucks, Rally Cars can have something crazy like that Bullet Farmer Dodge from Fury Road, and even bikes can take a tracked spin with Sd.Kfz.2 or that crazy Alliance Chopper - like, who cares if it would actually suck on the road. We have Atlas Earthquake! It's Motorstorm! Rule of cool rules everything!
The ideas are really limitless, but I prefer not to dream about games that are dead and gone - they won't happen. Besides, it is always as easy to imagine as it hard to make. But just to pick a couple from the top of my mind? Well... Californian forests, complete with wildlife, mudslides and forest fires that can start with a vehicle exploded in a wrong place. Sibirean wilderness with swamps, mists and frozen lakes that give way under heavier vehicles. But playing Arctic Edge at the moment, the next place I want to go is some kind of paradise island with tons of water, deep and shallow, driving through the huge ships of all ages who were careless enough to pass too close to the shore and stuck there forever. Jet skis and boats could be an actual classes, and amphibious cars could make an appearance. Trikes! Major Payne! Crazy quad choppers! Turbine cars! Flying cars!
And so far I'm picking up only real-life concepts, not even straying into the craziest parts of my mind. Honestly Motorstorm ended way too early. It looks like they've only started to realize what they can do with things like Atlas M-SUV and those Arctic Edge classes. Then, out of sudden, we go into the plot-detailed Apocalypse - which is, honestly, alright, could serve like a nice transition - but, sadly, it just ended there. If new Motorstorm will ever be a thing, I just hope they will go back to the roots: festival, music, racing. No need for a plot in a game like this.
Also, does Dmitry Molotov appear in Apocalypse? I'm starting to have a rivalry with that guy, really hope he will be in A when I'll get to it.