50% of Xemnas actions were subconscious behaviour orchestrated by Terra in a desperate attempt to find and reunite with his friends.
Terra's memories would often meddle with Xemnas motives and cause him to temporarily lose sight of his goals, made even worse by the presence of a Ven-lookalike (Who, according to Kingdom Hearts Ultimania also serves as vessel for Vens heart, to top it off.), so its not that far fetched to assume that all the things that dont make sense in context with Xehanorts motives were the result of Xemnas following urges from Terras memories within him. He also personally came down to Twilight Town to pick up Roxas upon birth and name him. Why did he look so satisfied, however, upon saying A New You? Possibly he believed simply by giving the boy a different name, he could cut his associations between him and Ventus, an attempt that ultimately fails when Roxas develops a personality a lot more reminiscent of Ventus than of Soras. Xehanorts and Terras motive were in constant war within Xemnas and Roxas unwittingly made it even worse, cause Xemnas to end up following actions to two different ends which conflicted.
Coming to visit Roxas when hes fallen unconscious? Most likely Terras doing. Talking to Aquas discarded armor? Clearly Terra. Searching the Chamber of Waking? Terra, trying to find Ventus. Showing disdain upon being called Xehanort by Sora? Terra. Asking Roxas if he remembers his true name (Note that, interestingly, he said True name not Old name)? Terra, hoping that Roxas would reply Ventus, rather than Sora. He didnt, unfortunately. (Maybe getting the correct answer would have caused a strong enough reaction to overthrow Xehanorts motives for good, though that is just speculation.)
Finally
Xemnas, trying to rip out Soras Heart during the final boss fight against him, asking if he Could spare a heart. Remember, the Rip-Out Move is one of the most time consuming ones Xemnas has, it leaves him fairly vulnerable to Rikus attacks and only takes out Sora, as opposed to him & Riku. Why would Xemnas do that? Did he want Soras Heart? It makes more sense if you remember that the heart that Xemnas is trying to extract could just as well be
Ventus. That move is an attempt of Xemnas to channel Terras despair and stubborn desire to regain his friends and misguide it in a way that will ultimately benefit the MX ideals: Here
Heres your friend. Come and get him. You just need to crack that shell open and destroy it. Come, we will work together and free him from that shell
Sounds like something MX would do to trick Terra, doesnt it?