Warlords!
 

The Emperor has died without an heir and the Empire dissolves into sectors, as each Sector Governor carves out his own Fiefdom and attempts to seize the Empire.

You would start with a number of races of three basic types:

Fringers, with lower technology, but more military resources.

Interiors, with Higher economy and technology, but fewer ships.

and Core, where perhaps you have a larger NPC empire to play what is left of the Empire.