Bingowings said:

...The mock-up was originally for a coda to Episode One.

Sidious pulls him out of the pit (to be the source of the clones) but he switches sides and becomes mysterious cyborg General guy (who claims he wants to kill the Chancellor/Sith Lord for setting him up for a fall).

...

This might have been a cool addition to Episode 1 that could mirror Palpy finding a crispy Anakin in Episode 3. Maybe Maul could be even more damaged by the time he gets to the bottom. For Maul to have survived Obi-wan's beat down, the wound would need to be cauterized by the lightsaber. Even cut in half, Maul is still a lot more intact than Grevious is by Episode 3.