I asked this in the PSA thread, but it applies at Mesa as well.

If an FO upgrades out of seniority order, what events can push him/her back to FO? Obviously, your standard displacement bid can do that. But, as more senior FO's log their 1,000th hour as SIC, can they immediately upgrade and displace the CA's junior to them?

Additionally, as more CA's are needed in future upgrade bids, can those FO's with their 1,000th hour logged upgrade and displace those below them?

I'm envisioning a scenario in which the company stops needing CA's, leaving CA's who are junior to FO's in place for years.