I agree that if we really need a warm body ready to play for that year (in case if Pyne transfers out, etc), there will be any number of serviceable QB's in the transfer portal for that 2023 class. I don't think any of them would be able to snatch the position from Buchner, but one of them could be a reliable option at QB2 or QB3.
As you stated above, we have three QB's who look like they can step in and play, and that at least the majority of the playbook would be available. All three QB's have at least a decent arm, and understand the game, and all three have at least some degree of mobility.
It's not like most of the Brian Kelly days (aside from 2015, 2018, and to a lesser extent, 2021) when you'd have one battle ready QB, and after that, it was basically a "don't hurt me" type of game where he'd minimize the playbook. For that matter, when Tommy Rees was playing, the playbook was cut down to 1/3rd of what was normally available (no rollouts, no QB runs, no medium or long range game).