You could make them capturable and distribute them all over the map, just like v-bases now, but I'd put them in the rear fields, and set to aim (with historical accuracy) and fire at enemy fields & strat. Only the countries getting steamrolled could benefit (as much as you could from as much accuracy they had) from the extra free offense, and it'd drain the steamrolling force to engage the rockets in the air as well as their launch sites on the ground.
It would also make for an extra strat target for level bombers, etc.