All of this seems like pretty farfetched speculation. There doesn't seem to be any hard evidence that Jeff would even want to lead the Beach Boys band, let alone that the Beach Boys would want that to happen. I agree with the person that said that Al would make a good frontman, although I'm not sure he'd want to tour as extensively as Mike & Bruce do.
& Al *was* a good frontman when he toured with Family & Friends band. 