I could do but it then loses invertibility. Granted with a bar that big it'll probably get itself back over with that, but in a worst case scenario when I don't have the bar, I'd like to be able to push things about a little bit. I guess 4WD (with belts) could be a thing with some major weight saving but I can't imagine it'd help too much...

Tiny little bit of magnet downforce round the wheels and some driving practise might help solve the gyro-ing though! I think you'll always get it on vertical spinners like this, it's more learning to deal with it than negating it entirely I think... gyro effects shouldn't be too bad at lower RPMs and if I get a motor that allows for quick acceleration I'll just stick the power on when I'm lined up!