My point with both Ronaldo and Best is them having to buy into being automaton in terms of what Pep demands instead of the freedom of expression they both thrived in where they were allowed to do their thing with no reprimand.Now clearly Best quantum-leaping from 1967 into the start of a City match today would be a compatibility problem.
But my take is that Best playing more freely then was as much a product of his time, as it was a reflection of the man. This is a time when there was far less - if any - patterned play on the training ground, the sort of which changed Grealish from freestyle individualist at Villa to team cog at City. Also a time when there was no real and comparable appreciation for the value of tactical systems and positioning which didn’t come until the 70s and beyond. So Best goes out onto the park with a different tactical view in his head then, than he would today.
If Pep could call upon this pool of legends all at their peaks and work with them for a few weeks, I think Best is one who could make the transition better than others. Some would struggle with the short-game demands. But Best is one of the greatest dribblers of all time and the one thing Pep prizes in his wingers is their 1v1 ability. Beyond that all he’d ask from Best is plenty of graft (which he generally had) and a wide starting position (which he’d pick up quickly on the training ground or watching a couple of games). Recognising his other-worldly talent and personality, over time his role might evolve like Messi’s did, from the traditional wide gig, to a false 9 with the freedom to do what he wanted.
Messi's thing; Ronaldinho's thing or De Bruyne's thing are all extremely conducive to the team itself as all of them are all about aiding others whenever they could/can. They're not soloists of the same ilk as the aforementioned, so you can see how they would be reserved their space in a Pep side. Is Pep going to be OK with Best holding onto the ball and doing whatever he wants in the way a Fergie or Busby were? I don't think Pep has had a single player of that ilk in a team of his? I agree with you about Best's tenacity on both sides of the ball, btw. In that sense he's perfect for Pep.
Of course, if we're talking about some time chamber where both come up under Pep, it feels like a different discussion (to me), but just plonked as is, in their primes, I think you've got too much personality and individualism there for either party to tolerate the other's ideals. We know Pep doesn't tolerate difficult personalities, and I don't think either player takes too well to being told what to do to the extremes Pep takes things to.