Nobody is being excluded. They can come to HS/LS if they want content.
Also: lorewise, the trigs are invading empires, not unclaimed space.
Empires have not replaced their navies with Edencom; they defend their territory with their navies. They don’t withhold non-Edencom forces for trigs and exclusively use Edencom when confronting them - they throw anything and everything they have. Also: Edencom is a relatively small group, so it is not sensible lore-wise for them to appear en masse. That would be like suggesting the size of the US Navy SEALs is on par with the total size of every police department across the nation. It doesn’t make any sense.
It’s not their fight
It’s not the target demographic for invasion
Unclear on what you mean here - elaborate?
Why? How is this enhancement better than alternative enhancements?