One of the things I think is important to a successful manager is familiarity with the club and everyone around it.
Familiarity with how things are done, what is expected, the "culture", the people, the opponents, the past matches and tactics etc..
I do think Pep's technical excellence does not guarantee he would make a good manager, but everything around him is being setup for that, and it looks like he is being groomed- or perhaps Jurgen being Jurgen- believing in empowerment and improvement, he just hands him the responsibilities of the League Cup.
I think stepping from the outside in for a manager, may make it harder to succeed than being promoted from within (BUT AFTER PROVING YOURSELF and Pep has already done that)
Pep's got another advantage in that he knows that he had been partly responsible for the success at the club- and the winning football the club plays at all ages, is due in a small part to him.
Otoh, promotions from within can also be disastrous, BUT a lot of times, the incumbent isn't as dedicated and committed as Pep or have been exposed to, or given the same amount of exposure as Pep has seen.
Pep's already being exposed in a supportive, calm environment and importantly- a successful environment, to Management (contrast to his short stint). You don't get to brief the press ahead of the manager, before a game if you're in ANY other club. (and what with a successful manager at that?).
The only thing that really is a danger and an unknown is how he will he respond at his first period of prolonged disappointment and run of not-so-good results. That's the big question for me. How will he respond to it and how will he get out?