Variable Civilian Protection Demand.
In My latest game, there is a backwater system, bypassed by better real estate further down it's warp chain, and being only a single jump from Sol meant it wasn't even required as a fuelling depot. Suddenly it became a front line system when one of the xeno scum races suddenly appeared through a previously closed warp point and proceeded to kill everyone and everything in system. Luckily being a single Jump from sol meant Home fleet could quickly deal with the situation. Home fleet left sol to deal with the incursion, leaving behind a squadron of ageing cruisers well overdue for refit, to mollify the populace.
I think in a case like this the people and politicians of Sol would be screaming for that Home Fleet to stay exactly where it was, and more so now as the war is suddenly next door. So I'm suggesting a series of Modifiers to change the civilian protection demand, - modifiers per enemy combat loss, +/- modifiers for range to nearest combat, +modifiers for own combat losses etc
This would of course, also depend on just how much unrest a garrison troop can deal with - is there a limit?