That sounds like it should be a fairly badass setup while retaining near stock reliability. I've never seen anything with the "butterfly box" modded, but I agree it should be a better setup if done correctly than a throttle body spacer.

You might want to invest in a mild port and polishing of the stock H23 intake manifold to free up some extra airflow, you might actually achieve better power gains in that setup than switching to an aftermarket one.