Rommel pulling a Vlassov in the west is actually a -very- interesting option. And certainly being it's him, lends a -lot- of credibility to such a thing.
I don't see that working. First off, Rommel would be an unlikely person to do it under the berst of circumstances, but that's another story. Even if, though, the first problem is that the western Allies would be unlikely to accept him in any capacity other than prisoner. To them, he was a dangherously capable Nazi general who had just put their troops through the meat grinder again, not some vaguely reconciliatory, chivalrous former foe. The Rommel myth of Mr Clean-War-Not-A-Nazi is largely a postwar artifact.
Secondly, they had little to offer. They had very little shared ideological basis, and what they had - a vague commitment to national self-determination and democracy of sorts - would not motivate Rommel to a sudden conversion. You could argue a second-tier German general had seen the truth of Marxism, but of - what, "United Nationism"? Hardly.
Thirdly, their Rommel could offer nothing attractive to his men. The Allied war aim at this stage is unconditional surrender, with the borderline genocidal Morgenthau plan in the filing cabinet and no great expectations of any future for Germany. Nobody intended to create the FRG, so basically, it's: "Come over to the Western side, we'll not ship you to safety but ionstead send you back to the trenches, only this time when you get caught you get a bullet from your own side, plus, your family goes to Dachau. But anyway, I'm pretty sure they won't shoot all of you after the war, and they probably won't castrate you, either."
The word you are looking for is "surrender", not "defect". He could have done that. Other German generals pulled it off.
