It’s clear they intend to force upgrades on new hires. There are several outs that would free someone from the Upgrade Games
A) not being sent to training on time
B) “extra” people wanting captain slots on subsequent bids. There seems to be a lot of effort around limiting the number of captain slots offered so the company can’t game the system. ? If it works

As for how they will offer such slots… making an entire class go to mandatory upgrade seems both really poor optics and a potential logistical challenge. But if they have 50 open captain slots, I don’t see anything preventing them. For now, anybody under 40 probably should be prepared to spend a two-year mission in Newark.