I'm not a Penn lover at all...But...
I do believe he would stuff the shit out of Khabib's takedowns. Khabib relies heavily on a single leg that he usually fails in the center and usually gets better odds after backing the other guy against the cage to finish it.
This is the exact type of wrestler BJ was good against.
...
BJ is amazing at defending the single...And if you watch his fights against all those wrestlers who got him against the cage...They had an almost impossible task of getting him down from there.
I agree with everything you posted.
Clowns talking about Khabib's unbeaten record and how "the sport has moved on" are cute, but they don't know their history, (and have clearly not watched Tibeau/Khabib). BJ faced bigger, better wrestlers than Khabib. He beat Hughes twice, he beat Diego into a bloody mess, and arguably beat Georges in their first bout. Penn's cardio issues and inability to deal with pressure, were largely a myth, stemming largely from poor commentating on Rogan's part during the second Hughes bout, where Penn tears cartelige in his ribs going for a sub and Rogan somehow interprets that as gassing.
BJ was among the very best at defending the single. Look at the first round of the second Georges fight: Georges literally brought in a medical team to help him gameplan for the bout, and focused 80% of the early entirely on nullifying BJ's ability to breathe, to starve his muscles of oxygen. But Penn still spends three quarters of the first round on one leg, stopping 7 or 8 takedown attempts from a much better grappler than Khabib.
When GSP finally gets him down in the second round, he puts his knee on BJ's midsection, to prevent him from getting a big breath, and doesn't work sub attempts--Georges only had his black belt from Fernandes for less than a year, and said he didn't want to leave himself open on the ground. St. Pierre works the ribs and actually strikes Penn's shoulders, to drain the blood from them and keep them oxygen starved. His medical team told him it would pay off in later rounds, and it did.
Khabib could try to replicate that, but Georges has 100x better fight IQ than Khabib, not to mention a huge reach advantage over Penn.
If Khabib were to look for the single against a 2006-8 BJ, he'd end up like Diego. Penn could literally ignore the standing feints for takedowns, and would expose the holes in Khabib's standup. If the fight did go to the ground, it gets more interesting, but I'd still give Penn the edge in pure grappling, he was as dangerous off his back as Khabib is, anywhere.
It's a fight I would like to see, but with the current state of both fighters...It would be a meat grinding slaughter for Penn. He would look like Chuck or maybe worse.
Absolutely. Today, it would be a horrorshow, and Penn would get killed. But 2007 Penn would make Khabib look amateur.