Of course that depends not on their business model, but completely on how much revenue they could generate. Such compliance likely isnt cheap and therefore this is a perfect illustration of my point: bitcoin simply isnt ready for this. The economy is way too small and we have way too many exchanges and other speculation tools (and too many speculators (ab)using them) for what is mostly still a nonexisting economy.
I largely agree with you on that. I doubt that any of the exchanges which existed before the Bitcoin bubble had planned for such rapid growth. They probably weren't capitalised for it and so are entirely dependent on revenues to fund it (they could raise outside capital, but that's another story).
There's no excuse for new exchanges to have the same issues though. It's ridiculous to start a new exchange now without enough starting capital to fund proper security, regulatory compliance, etc - such ventures deserve to fail. I'm not suggesting that it would be cheap - on the contrary, I'd expect any new exchange to have a minimum of several hundred thousand dollars in start-up capital - but it's crazy to start an exchange on a wing and a prayer now and simply hope that revenues will cover both your initial investment plus your ongoing costs.