Didn't know that was a thing, but I like it!
That could work. Or maybe the Mask of Life (if it's on Artakha) could revive them just by being close to them, which would reignite the battlefield.
For the sake of the presence of lawful justice (trial through Axonn), Umarak could be imprisoned (the warden being Hydraxon). He would be depowered at this point (no mask), so he'd be imprisoned until the appointment of his execution (via Umbra).
Vezon might be pardoned, or serve a less extreme sentence. He'd lose his mask and spear, of course. In the event he is released, he'd be under supervision of Umbra.
Yeah, that's kinda dark. Not a happy ending for evil. Thinking about it, Mata Nui wouldn't really be in a different timeline since He pretty much invented it (Mask of Time being a fraction of His power, after all).