Do you really think CX would let anyone sit in the left seat
Absolutely not. For all their faults (and there's a long list) the FOPs flying & training managers don't & won't give out commands willy-nilly. In fact, with the inexperience in the cockpit these days the job of a CX captain is getting harder than it was when everyone joined with 5000 hrs.
Now, if you'd asked "Do you really think CX would let anyone sit in the right seat or SO seat", then I'd answer YES. The bean counters don't care - it's all spreadsheets & no responsibility for them. The burden falls on the captain, and it's his/her responsibility to manage these "anyones" in the cockpit, and the captain that suffers the full weight of responsibility when it goes wrong.