Well the defenders will have to move out and intercept before the enemy gets there. Otherwise it does no good to kill the bombers after the bombs are gone. Bombers would get bonuses for landing (to encourage nursing woudned rides back home) or limited craft (for same reason). The attackers have a 360-degree path of attack. They can plan what they want, including feints and false radar signatures, including breaking up the escorts into several groups to distract the enemy. The enemy can do the same, spread out as far and as fast as possible to scout the enemy main group, but they have to watch their gas consumption because it takes a while to land, refuel, and climb back out.
You're probably right. It's probably too limited for a full scenario.
How about upping the start hardness a LOT, and having frame 1 require them to bomb 5 strats closest to them. Then IF they bomb enough, they can move to the next targets, and IF they move in far enough by frame 4 they actually can take down the HQ building. Again you'd have to up the hardness to really make them work for it, but I think there could be a good balance in there somewhere.