Bit of a straw man there. No one here is even vaguely reacting like that. And nor should they, as it's a fair, if somewhat minor, question. There are and will be many, many threads about the different coaches, players and tactical analysis. This is one which this is interesting, though slightly less fraught than many will be.
As for the question at hand, if Mariotta is ready to be a backup, then he'd be my choice too.
Otherwise, I'm not sure out of the many others, who would be suitable as an upgrade but also willing to be a backup.