One I've had puttering around the noggin for a while.
Your researchers may only research "civilian/infrastructure" type techs. Missile reload, weapon calibers, etc are verboten, except when there is a war. Then all research is available. When the war is over, back to the civilian only research. Research in progress when the war ends may be completed.
Ships may be designed, but only refits may be done in peacetime (under 50% cost). Only new construction would be civilian (grav survey count as civ for this purpose). The only new military construction that may be done is when a new sector command is created. Planets use PDCs and ground troops for protection.
Troops may only be created in sufficient quantity to garrison colonies.
Any thoughts on what the starting parameters should be? NPR count, etc? And any other restrictions you can think of?