I think you're right though - holding out for the one that's going to not only put in the time, but be rewarded with a fair founders share and (more importantly) see the product through to it's natural conclusion is the way forward. One more road block seems to be finding someone that wants to go from hacker to team manager.
Either way, and your FWIW is noted, we'd have to create a situation that either sets up a barter contract, an IC agreement that leverages a valuation on time, or create founders agreements that track the input toward future payout (basically what we're already doing) if we invited people over. I think any of those paths would forego any US lawbreaking since they'd be non-employees. It just seems like a lot of legal review (fees) and hassle though vs finding the one engineer and knowing that the partnership and mutual expectations are aligned.
Aloha~