Just to throw two cents in about Legio: remember that they are, in the main, designed to be an anti-player "super-boss" and extra challenge for you to take down. As such, a lot of their ships are designed to fight against specific player gimmicks, such as using tons of capitals or trying to rely super-heavily on carriers. Solutions that would work in the main game are, purposefully, much harder to use against the Legio and you'll need to change up how you play and how you build your fleets in order to fight them.
(Some of the side effects of their design are why I have some issues with their current implementation, but what I'd consider "proper" implementation is far more work than is reasonable to ask of Nia in a ship pack mod and is why you can turn the Legio off.)