You ought to cross post this to the Karn Forge thread, where I think you'll get more traction.
For your idea....I don't think it's bad idea, in that it's a legitimately castable spell that (1) the academy didn't even discuss and (2) is an effect that Karn Forge actually wants. However, it has a few problems. The biggest of which is that it's grid with suspend. Giving people a turn isn't the best idea in Vintage right now. While I'll freely admit to starting a lot of games with "grid, go", you also want the ability hit 6 mana on 1 (not the craziest thing in a Workshop+Grim Monolith deck!) and Grid+Threat your opponent. What I do think makes more sense is a single Hope of Ghirapur out of the board, if we're playing one at all, as a wishable Grid effect, which more-or-less ensures that you can set up for the follow-up wish for Lattice to end the game.
Also, re: the finals against Joe--I'm pretty sure I'm a big favorite if I hit mana off my top 3 draws, instead of more Karns. The problem there wasn't that I didn't have a grid effect, it was that Joe (very wisely) cut me off mana instead of trying to fight threats.