To add to this.... I'd love a really hardcore MILSIM event. As close as possible to the real deal as feasible.
That being said, if you took a truly MILSIM scenario and broke it down, I think most (not all) Airsofters I've ever met would shy away from that. Most guys and gals out there don't think too much of spending hours on end up to there arm pits in stagnant swamp water just get the drop on the objective. Come to think of it, I don't either.... but I'd probably still do it ; )