Ooh, a Lotus Petal. Or perhaps a single-use Mox Diamond or Chrome Mox which undoes the card disadvantage at EOT. That's really interesting - makes it much less good for single-turn instant-win combos (which is a good thing), but the cantrip on Jury-Rig means it's not painfully bad card disadvantage (just moderately bad card disadvantage to the same extent as Lotus Petal or Simian Spirit Guide).

Very cool. The only downside I can see is that the two modes of the card have so little to do with each other, like Serum Powder. But at the same time this is about the only way that a Jury-Rig mana rock could look.

Jury-Rig is still a very interesting mechanic, I think. I'm excited to give it some playtesting.