I like the idea, and have actually thought of the same, but never thought DRO would fit - the missions aren't made for it.

On that note, DZO would be awesome! You could have specific zombie ops, like "Save this civilian deep in Z territory", or, "Defend this outpost against a horde until the chopper evac arrives", or "Your team must break out of this city and escape the island", etc...

Imo item extraction from crashed aircraft or sample collection would be pretty rad, but escape WOULD BE SICK, its gonna be resident evil all over again.