Can Mitt Romney sucessfully rehabilitate his image at this point?

[Absentee Voting Ghost of Ruin]

I am not a Romney fan, but I don't think he's quite as bad as you describe him. Although, he's still a damn poor nominee and lacks any real strengths as a politician. Contrast him with W, who was a very poor candidate in many areas, but had the whole 'folksy charm' thing down pat.
I think that the voting public's perception of him could be changed, but it's going to take a big change in how Team Romney does business.

So far, he won the nomination via heaps of money, establishment shenanigans, and rivals who could at best be described as lacking. None of these are going to be nearly as useful in winning the electoral college. I see very little evidence that Romney is willing or able to re-brand himself as a person. (As opposed to his political positions, which obviously change with the prevailing wind.) Only if Team Obama is foolish enough to let him reinvent himself on the national stage will Romney become a credible candidate for President. (Unless the economy is teetering on the verge of collapse again, in which case Romney has a shot simple by virtue of not being Obama.)

[Absentee Voting Ghost of Ruin]

IMO, what's most frustrating about his "image problem" is that it doesn't seem nearly as prevalent and damaging as it should be.

I agree. I look at Romney and I see a clueless vulture-capitalist who will say or do anything to get the position he thinks he's somehow entitled to. Fortunately for Romney, this view of him does not appear to be widely shared.