I just think that a primetime 68-72 Bad Bennie would have a real chance of beating Hagler. {who I admit I am not a big fan of} I just think Bennie at that time was easily 10x better as a fighter than the version Marvin fought in '78. He {Bad Bennie} had nowhere near the power and reflexes of prime Bennie when he was losing later fights to Antuofermo and Hagler and Love, etc....
I wished you were right...I think Bennie still comes up just short. He had the misfortune of being around during the Monzon/Hagler years or we might remember him differently. I think he is still just a hair below them. I won't say he couldn't beat Hagler (close) or Monzon (never saw their draw?). I just don't think either one is the likely outcome. I would give a prime Willie The Worm a better chance against Haggler (Oh, wait a minute, he already did that!).
Hagler would have pretty much used the same long right jab and lateral movement he did when they actually met. Luis Rodriguez and Rodrigo Valdes had his number. Bennie couldn't beat cuties Curto and Griffith in Philly. I think Marv would have always stuck and moved against him, and Bennie wouldn't be able to catch him enough to win a decision, let alone force a stoppage. In 96 bouts, Bennie lost 23 decisions, some of them to outsiders in Philly [like Joe Shaw, Rodriguez and Griff]. His SD loss to Vinales in Scranton is disturbing. He had to avenge a goodly number of defeats to first time opponents. Hagler wouldn't have opted for war against Briscoe, he'd keep him in mid ring while circling the perimeter.