Filoni suggested repeatedly that it was Maul's survival that put the idea in Palpatine's head that he should not give up on apprentices right away, which is why he ran off to save Vader, whereas with Maul he took it for granted that he was dead and moved on. To me that implies that he was impressed with Maul. If Maul were just broken and useless, then I wouldn't expect Palpatine to so desperately try to keep Vader alive after being similarly crippled. In contrast however, Lucas is the one that puts forth the idea that Palpatine was disappointed with Vader after being injured and that Vader was never able to reach his full potential. So what Lucas had said and the idea that Filoni has pushed for don't really jive up IMO. Maul survives his injuries and impresses Palpatine to the point that he refuses to let Vader die, but then Vader is a disappointment. Palpatine is apparently disappointed with Dooku's age and power, which draws him to Anakin who is "far younger and more powerful." But during TCW it is not 100% certain that Anakin will turn yet, so he may not want to put all of his eggs in one basket. IMO there are two likely "uses" that Palpatine could have for Maul -keep Maul around and give him the chance to kill Dooku and take his place as a Sith once more -use Maul as a science experiment to explore how he survived and perhaps use some of that knowledge in the effort to keep Anakin alive -use Maul as a pawn to draw out Talzin -allow him to continue antagonizing Obi-Wan in an effort to kill him and isolating Anakin by killing his mentor Regardless, I don't see a shining future for Maul. If he's a pawn or test subject, there's nothing glamorous about that, and if he was being set up to potentially replace Dooku, well we know that doesn't happen. As for killing Obi-Wan, that seems like a non-issue after ROTS. Palpatine is said to be less forgiving than Vader, who himself is very ruthless. I would think that Maul turning himself into a rival and being bold enough to try and usurp Palpatine would not go over well. IMO using Maul merely as a test subject or to draw out Talzin make the most sense to me. Giving him another shot at being a Sith or giving him the autonomy to hunt down Obi-Wan seem a little too forgiving and leave Maul as too much of a liability IMO.