Yeah, once you can draw your whole deck, you can keep drawing it even if mountebanking starts. But I'm not convinced you'd be able to ever get to the point where you draw your whole deck if your opponent spent his first two $5s on two mountebanks, and then labs afterwards to draw them more of ten. You'd just never get to that point. Something simple like mountebank/money with a few labs is pretty brutal at shutting down engines with weak trashing.
Also, for what it's worth, Trading Post replaces two cards with one, so in terms of drawing your whole deck, it only decreases deck size by 1. Good because it avoids making you spend buys on silver though.
Dunno. I suppose I'd have to try it or sim it to know for sure, but I'd definitely lean towards something based on mountebank+money rather than a draw-your-whole-deck lab engine.