You only get an upgrade if they like you and you're prepared to play their games.
They are scared most of the time to give you a command. It means you'll be gone to the majors after a short time. They also have to hire another FO to replace you which costs them two training slots.
Better to bring someone in over the top who only costs them one training slot.
Plenty of upgradable guys on the bras. Most Are ex charter types. The Metro and Dash seems to be the pay your way cadet fleets with the aces moving from Metro commands to Dash commands
Most guys seem happy that I know there however. Play it their way and don't ask too many questions and you'll be fine.
Go to work, do your thing, don't get involved in politics, accept your roster change the night before, accept a flying duty the night before and you'll be fine.