We'd love to get more track makers, so please do.
The rubber balls (or bouncers, as I like to call 'em) should be possible to shoot at least with bowling balls. I have done so myself on some occasions. The cakes don't aim for the ball yet, but I have proposed that they could do, so you have some easier means to kill them off. Another hint is that you can often avoid them hitting you by not driving in the middle of the road.
I am in the same boat: I don't do much for the project itself, but I've played this game for years and I love it and its community, and I try to keep up with development and come with constructive feedback as my way of contributing back.
There are a couple students working on AI at the moment, so hopefully we'll get smarter AI sometime (dunno how far they've come). So I am positive that we'll continue to see very interesting development to continue raising STK to its true potential.