I'd imagine it would be fun to have a multi ball mode with 1 real ball and 2 to 3 other virtual objects, bouncing and reacting to the flippers as if they were real, in conjunction with the real ball.

I'll be honest though, the concept of hitting a virtual playfield object with a solid ball doesn't sound appealing. You're going to need really great sound designers and animators to make those virtual impacts have some meat to them, even though the ball travels without impediment.

There's a psychological joy when you careen that steel ball off of an object with a solid hit. That joy will be absent and have to be recreated somehow via sound and image to create a tactile fidelity to the action.

Here's an idea for a game mode that's sort of like a iOS type of game. Imagine the playfield as a big texture of dirt. As the ball tracks over the playfield it digs up the dirt creating tunnels similar to Dig Dug. Then, once the game mode times out, water or some liquid (not real liquid, in the game screen virtual liquid) pours down travelling down your burrowed path in the dirt. If the water is able to pour downward to a certain goal or hole, bonus points are accumulated.

Yeah, kind of a weird explanation. But i think the point here is imagining the ball as a kind of eraser over the virtual playfield and how that can be used for gameplay.

My kids love that goofy game. Aside from that, there's some fun design things they do by using the finger interface as a subtractive element on the playfield.

That's probably a good idea. I'd imagine that you wouldn't want to jump the shark on your first outing.