I remember that Steamband start you on the bottom level, but in the sense of "inverted model", ie. monsters get harder and harder towards the surface. Starting on the hardest level is certainly an interesting idea. The player would probably have to start out with a lot of power that dwindle with time (maybe relying on consumables a lot, starting with a full inventory with hardly any way to get more, or some kind of exhaustion clock).
As always,
Minotauros