Any ideas on how to free a rusted ball on B&W hitch?

This issue is the one real weakness of the TO Ball, IMO, and one that we often overlook when cleaning our trucks. I wonder what would happen if someone machined a small groove about 1/8" or 1/4" from the bottom and put an o-ring in it, with just enough sticking out to create a bit of a seal? The other option would simply be a cap that covered the hole and extended down far enough to engage the locking pin. Downside to this is that you'd have to store the ball somewhere.

Lyle