I think you're absolutely right, that team would cruise past Luton. Unfortunately I don't think it's the one Pep will play.
I like most of the lineups I've seen put forward on this thread. It seems like many of us are wishing for a return to the team being fielded consisting of mainly the players who actually won the treble, with the new players being eased in one at a time.
That's certainly what I'd like to see. It'll calm the team down and allow the players to do what they know and start getting their confidence back.
However I don't expect that to happen. I expect to see Walker and Alvarez starting again (they shouldn't) and probably Doku if he's fit (it should be Jack), because Pep is stubborn as fuck and apparently determined to demonstrate that he has no belief in the saying that the definition of madness is doing the same thing repeatedly and expecting a different result.
I really hope I'm wrong though.