As with anyone here, I respect your passion and personal desires, but speaking strictly for myself, I'm fine with Bowser Jr. not using the paintbrush. The Clown Car is just so much more interesting to me in every way, even from a nostalgia standpoint where it harkens back to Super Mario World.
I know, I know -- whynotboth.gif -- but I think Sakurai will really take this Clown Car concept and run with it. Already we see the car waddling around on its propellers, burping up cannonballs, licking enemies with a comically huge tongue, and pirouetting through the air in a whirlwind of boxing gloves. It frowns when hit, as predicted, and exhibits amazing elasticity for a machine, stretching and swelling and contorting. I love how Sakurai took a "mechanical" concept and delightfully exaggerated it in cartoon fashion.
And possibly the best part is how it seems we'll be able to play as each of the seven Koopalings, as well, as per the original rumor from early August that lines up perfectly with this leak. The hit-boxes are the same thanks to the Clown Car, after all. And in that one screenshot, we see a trophy of Larry Koopa in the Clown Car. It's all coming together.