See, your problem is, you don't really have time travel, at least not when Lobsang acts as Time, because in that case, he would simply not allow for that. If he should not be acting as Time, Time herself would and if she did, he'd just call on her and tell her to stop granting anything to Ion. I'm sure mother would oblige.
The matchups were just the ones you proposed, I'm pretty indifferent to who is pitted against whom, as I am confident that any of my three team members can beat any of yours. If, however, you asked me for my ideal matchup it would be:
Ludd vs. Ion
Dr. Manhattan vs. Galahad
Eriond vs. Rhapsody
Lobsang would just stop time, break Ion down to his molecules and vanish into this pocket universe of his that is filled with chocolate (he needed it because a former Auditor wanted to commit suicide, he kept it because he really likes chocolate). Sir Galahad, meanwhile, can talk about his purity and attack Dr. Manhattan as valiantly as he wants, in the end he simply hasn't the means to stop the big blue one from eradicating him. Manahttan would take one look at Galahad's lance and it would be molten, just as Galahad himself would be shortly afterwards. My position on the matchup between Eriond and Rhapsody stands. Noone, nevermind how powerful they are, stand a chance to simply change anything about him. Half of his entire universe once opposed his being made a god and didn't succeed. Now this half also stands behind him. I have trouble believing that Rhapsody would be capable of beating any of the lesser immortals from the Belgariad (Belgerath or Polgara, for instance), let alone the one that is to become the one god.