That sounds just like the mission with the Krios' escape pods in the original Silent Threat, except that only had one wave. And it was nigh impossible.
You would, as Snail said, want to keep track of how many die, rather than just fail the player as soon as one dies. Although as far as bonus objectives, it seems like the pilot medals screen is directly analogous to XBox-style "Achievements". Some of them are kind of dumb, particularly in FS2, like Epsilon Pegasi Liberation and Nebula Campaign Victory. I mean, getting a medal for beating the game like in FS1 was enough, IMO, and individual missions not so much. Nonetheless, that would make for an awesome bonus objective and grant-medal sexp.