Rambam holds with the basic metaphysics as Aristotle

The Rambam holds with the basic metaphysics as Aristotle. But this leaves him in a predicament when it comes to power. Since the Rambam and Aristotle  say the God has no matter that would mean he has no ability to do anything other than what he is doing. You need to get to the idea that action does not use up possibility. 

What I am trying to say is what Kelley Ross is saying and what I think we have to consider as going for the Rambam is that universals represent a kind of mode of necessity.

I think that we can see why the Rambam was so firm that God can't have any physical aspect. Not just from a Torah perspective but also from the perspective of Aristotle.  [That is he is not specifically trying to knock Christianity or any specific doctrines. He just holds that matter and the universe is not a part of God. That is what is usually called Monotheism. Pantheism is a different belief system introduced by the cult that the Gra signed the  excommunication on to get people to worship their leaders.  After all if "Everything is godliness then mybe it does not hurt so much if their "tzadik"  leader is a little more godly than anyone else.]

As Kelley Ross writes:

 ..In Aristotle ... matter is potential; but then matter is so intrinsically amorphous, merely the passive recipient of actualizing "form," that the Neoplatonists identified it with Not-Being (and evil) -- quite apt when Prime Matter, or pure potential, is not actual at all and so in fact doesn't exist -- and both Aristotle and the Neoplatonists eliminated any material component to God (or the One).