747 captains are hardly junior these days...in the main. You downsize the Company, force draft guys to the jumbo if nec....they’d probably get enough volunteers anyway. And backdraft the guys that recently went to the bus. Very senior, all of them. If they don’t like it, well the door is always open. Someone has stolen it.
Lower ranks... s/o’s are easily trained. 777 conversion to a -8 fairly straightforward.
As you say all bets are off.