the loss of limbs doesn't make you less powerfull perse, but makes it impossible to use powers that are normally focused through said limbs (like Force Lighning). It seems there are certain powers you can only use when you still have living hands/limbs to act as a conduit for the Force. So it's not in the bodymass or the connection to the Force, but it's the limbs themselves.

Right after Savage kills Morley, Maul says the following lines:

"Through victory my chains are broken. The chains... the chains are the easy part. It's what goes on in here (points to his head) that's hard..."

The first sentence is obviously part of the Sith Code. The next two sentences are the interesting ones. Those same lines are said by the Son in the Mortis episode. In the second episode of that Arc, the Son is disguised as that odd, small creature in the dungeon with Ahsoka.

There's two ways to look at this. A) It's just a really cool reference to Mortis and the dark side. That's pretty likely. B) Maul is actually the Son in disguise!!

Darth Maul's return and Mortis - the worst inventions of TCW. The thought of them being combined doesn't change my opinion on them.