Probably set around this time frame.
They're running out of larger ships and transitioning to smaller ships. There's a time gap there if relative peace (raiding) or they can be used as a distraction.
No super weapons, Dark Jedi, Sith etc.
Context at the time frame I'm looking at there's multiple factions.
The Imperial had the deep core. It had massive amounts of star destroyers, super weapons, the clone emperor, super star destroyer s etc.
Luke and Co smacked that flat. The Imperials withdrew to the outer rim including...
The rough idea would be they're in a weakly held sector getting preyed on by mysterious raiders.
If it's imperial they will likely be pilots on one of them in a reverse far orbit game where they pirate the New Republic.
Far Orbit was a campaign adventure where they play on a mutinous...
It's Star wars though, see rebels, First Order, Palpatine etc.
They've had larger secret fleets. A million people is nothing in Star Wars.
It's less people involved than WW2 logistics.
It only has to be vaguely plausible. It's less than a sector fleet and there's a lot of sectors.
Star Wars has fortress world's. I'm not sure if this is a sector level threat or galactic level.
100 cruisers requires 200000 crew. Look at WW2. A single planet could build and crew that many. Hell Australia can crew them.
200 of them is more firepower than the Imperial fleet at Endor sans...
Hidden base, thinking of a somewhat normal world with a moon that can be mined.
Or really inhospitable with an orbiting station. Inside or near a nebula that's really hard to navigate if you don't know the path.
Game srat wise strike Cruisers are really nasty.
Supplies don't really matter as they have something like 2 years worth of supplies.
Space is also very big and hyperspace let's them teleport essentially.
Depends what the precursors tech does.
In the upper scale I look at megaengineering (dyson spheres, ringworlds) and giga engineering (building star, solar systems, black holes etc).
If terrorists get hold of some facility like that and they can reuse it.