Romney can certainly rehabilitate his political image. More people will be paying attention to the general election than the primaries, so he will be able to shift more to the center and successfully erase the "severely conservative" meme somewhat.
I dunno, I think he'll have a hard time shaking the "severely conservative" meme.
His problem is not "severly conservative." People who've been paying attention already know for whom they're going to vote. His problem is that he's not charismatic. The wishy washy middle has to be inspired by platitudes. I don't think he has it in him.