BattleTech AU: The Under Sphere

Some years ago I struck on a number of ways to procedurally generate alternate campaign settings from existing BattleTech material. My third and favorite is an underworld where people, 'Mechs, factories etc appear when they die or are destroyed in the Inner Sphere.

An obvious consequence is that characters or regiments who were killed off are still knocking about; or less obviously, in the case of conquerors and assassins, they quickly find themselves outmatched by vengeful victims and get killed again. So the ownership of planets tends to lag by a war or two, and many of the little alliances from the 2300s and 2400s would still be around.

It's my favorite because it lends itself to...