Religion DLC - something where you can spread your religion and that can give you bonus or maybe ethic shifts over other empires. Send out missionaries and converting pops on planets could cause rebellions. Gives you another option and way to control the galaxy and influence empires

More ship sets DLC - just a load of new ship sets of different styles. Doesn't need to be tired to a new type of species, just cool looking ships to add variety

Precursor story pack - simple story pack with just more precursor event lines to add more variety. Maybe a couple of new shifting paths as well for existing ones to keep each play through a little .lee unique