That would be quite a folder!
If you're up to making your own studded tires, I don't see why it shouldn't work. You'll just need to find some decent knobby 349 tires... and go from there.
The Mu SL is a nice bike. In fact, Dahon makes a number of good bikes that would be worth a look. Since you might be going with a 20" bike, it might also be worthwhile to check out other makers like Downtube.
--sam