I always like the idea for a freemode in the Empire at war remake mod.

A mode where you can just create your own fleets and let them fight eachother.

Some mods already have this like Thrawns Revenge's instant fleet builder or the Unofficial empire at war remake 5.0 mod with freemode.

A freemode in this mod could also allow players to test sertain strategies, fleets make-up and the negatives and positives of different ships. But besides these factors it would mainly be just a fun mode for players that want to make they're own battles.