... I think it could be a good idea if it was a transformation. Giving Yoshi a new moveset and making it a lot more powerful but with one massive drawback. Once you get hit baby mario gets into a bubble and you need to catch it, otherwise the opponet can attack the bubble and damage you!
It would be a mess though, a 4 Yoshi match would be crazy.
"I've Underestimated the Horse Power from Mario Kart 8, I'll Never Doubt the WiiU's Engine Again"