I think the ships & charaters should be unlocked from each other.
This would allow high ranked charaters to fly whatever tier level of ships they want to.
And bridge officer type slots & console slots should be based on charater rank, not ship types. This would be a natural blaance to the game.
Your charater is Tatical officer. as this charater moves up in rank they are allowed a max number of bridge officer type slots. Independent from the type or tier level of the ship you want to use in the game.
This would also be done to weapon & consoles slots. The higher your rank the more Bridge officer, Weapons slots, Consoles slots, you can use. So they are NOT tied to your ship type or tier.
This should be easy to do in game and this would allot everyone to fly the ship they want and have that ship play the role in the game they want it to.
Take the Galaxy X is a Dreadnought Cruiser. With this idea. You can turn it into any ship type you want. Maybe you want a Dreadnought tatical ship. Well all you would have to do it assign more bridge officers and more weapons to your ship. That number would depend on how much rank your charater has and how many bridge officer & wepons & consoles slots you have earned the right to use.