simple ideas and guidelines.
1. not everything needs missiles
2. 360 degree turrets should be a rare feature
3. you need weak ships, normal ships, as well as difficult ships, otherwise it just becomes an exercise in futility.
4. not everything needs it's own faction, once you get too many factions and their fleets all spawning normally, the game slows down on weaker PCs
build up existing factions, add new ship designs to the randomly spawning fleets.
these are just a few observations I've been making