[Phyrxes]

A couple thoughts:
Although similar to a football a rugby ball would work if we are thinking "major" sports.

I would expect bowling balls or anything heavy would add some form of pad under the field to help mitigate floor damage? I'm envisioning a school Activities Director freaking out over the idea of a robot dropping a bowling ball on to carpet that is sitting on his basketball court.

Next year's senior class will have seen tubes, basketballs, and discs; they haven't seen been involved in a "max capacity" or "large object" game.