Xenmas may have wanted Sora and Riku to slain him that way he or someone connected to him could come back as powerful as ever. In order to do this he asked for Kingdom Hearts power and treated it like a god and then fused with it. It may have been his truimph card. With a mind like MX it seems like an genius idea. Now with the time theory.
When Xenmas confronted Sora in KH FM he tested and took some of his memories and thus this created Xion. In BBS MF goes to challenge TAV. This is the same motive Xenmas did except I don't think MF took memories though. So MF is connected to MX therefore linked with Xeohanort. For whatever reason both test their opponents. YMX has all of these abilties from Xenmas, MX, and Terra, it seems and may use it to his advantage, but of course he may need people to help him out. it sounds like to me he wants to become god and control the worlds.
Now with the keyblade we are not sure if he choses to use it or not.
When Xenmas confronted Sora in KH FM he tested and took some of his memories and thus this created Xion. In BBS MF goes to challenge TAV. This is the same motive Xenmas did except I don't think MF took memories though. So MF is connected to MX therefore linked with Xeohanort. For whatever reason both test their opponents. YMX has all of these abilties from Xenmas, MX, and Terra, it seems and may use it to his advantage, but of course he may need people to help him out. it sounds like to me he wants to become god and control the worlds.
Now with the keyblade we are not sure if he choses to use it or not.