That first idea reminds me of some of the tracks in hot wheels stunt track driver 2... not gonna lie
That doesn't make it any less awesome sounding though!
Also, as far as the tiny tumbleweeds are concerned, perhaps if you hit one, you get a weird bonus of some sort... like in the game snowstorm back in the day. There was a rabbit on the one track that if you could manage to hit it (it was nearly impossible) it would give you something like 1,000,000 points or something ludicrous.
I dunno, just a weird idea...