While I agree with you that he hasn't helped his case by continually lying and contradicting himself, I'm not at all sold on the notion that if he'd come clean at some point, he'd be in. I feel like it would have just been a ploy by MLB - if he confessed, it would have been "HA! WE KNEW IT!! SUCKER!!" and then hang him out to dry.
Either way, it should be up to the voters. If the Hall is going to have a rule that they won't allow players under ban to be inducted, then MLB needs to lift these bans so voters can decide. MLB has allowed voters to be the moral authority on PED users, so why not gamblers too?