I ran a game set on the perifery where the Dixie Confederation had automated farms on an entire contenent still functioning,this led to great intrege as the major powers relied on it for much of thier food.I reduced
the forces involved from regiments to lances to represent the reduction of technology and also intoduced the Papacy,a puppet of Kurita,as the villians.Of course the Confederation had alien slaves.
Painted Grey mechs w/ a reverse Confederate flag and yellow 'gloves'
The Papacy had mechs painted like The Pope,Cardinals,priests and Knights Templar.
Used classic Battletech for mechs and GURPS for everything else
The ruling familly (the Lee's)were illiterate by choice