You said you might invent a crystal ball trick. Consider this:

How about building a small stand for your crystal ball that can be reversed for two reveals. Just lay a tiny revelation card, not glued. Palmed in your hand is another tiny revelation card. Force the two cards and have one person see their card in the crystal ball. As you do this, you load the second revelation in the bottom. As you turn the stand around, the first revelation drops into your hand and the crystal is now over the second revelation. flip the stand around again and hand the crystal ball over for inspection. Of course, you would need misdirection for each.

KJ