Correction: they are irreplaceable. When they leave the only thing to be done is find a new direction for success. It is possible that the post-Klopp era will be just as successful, but I doubt it.
I certainly agree that inadequate coaching of the team as a whole is a bigger problem than Ronaldo. Though I am in agreement with Wilson's piece that he can be more of a hindrance than a help.
Brucie? He's a better manager than Ole, is also a club alumnus, and could just focus on keeping things tight at the back, letting the expensive attacking players figure out the goals themselves. OK, OK, I'm not being serious, - but actually, I'd wager Bruce would not do worse than OGS with this squad.
Bringing in Conte means a full-on tactical rebuild that will take a season plus before we can expect to see it operating fully in his own image. So hiring him means skipping the caretaker bit entirely and accepting Conte-ball.
No idea who would be available and willing to be a caretaker...Frank de Boer could do it but probably considers himself above temp jobs. I vote Avram Grant.

Or Joe Kinnear? I would pay to hear him go off again like he did during his comedy stint Newcastle.