As far as backstory was concerned, How about this?
The federation, seeing the production time and expense of the Yamato class, was looking for something a little more versatile in a battleship. Taking cues from several different popular design choices, the Odin class was born. Named for it's ability to theoretically stand toe-to-toe with the empire's largest battleships of the time, and have a limited compliment of fighters (for a carrier, but having quite a bit more fighters than any other type of vessel) for both point defense and blitzkrieg tactics. The only downside was the method of construction. By using multiple design components from other ships in the fleet, and thus reducing the cost of production, the ships structural integrity wasn't what came to be expected of a ship it's size. As a last minute change, half of the upper hanger bay was repurposed, in it's place was the largest shield generator to ever be fit on a starship. Rivaling the strength of a small starbase, the shield system compensated for the excelsior level hull strength, and the Odin class was put into production. On it's third mission, it proved its mettle by destroying a King Condor Battleship with minimal damage to the Odin, the fighters proved a pivotal role in intercepting the plasma torpedoes before they could reach their target.