You might want to check out my own take at this concept, "Asteroid Attack" - it was made when the editor was still in beta, so it's nowhere near as polished as yours; but it does IMO do one thing very well.

That thing is "storm the beaches" style assault - an idea I had for playing Occupation mode where the defenders start off strong and get swarmed by constantly strengthening attackers. The short summary is that attackers get a range of spawns 3/4 surrounding the bomb target, while the defenders get a clustered and very defensive spawn fortress with lots of cover, sniping positions, obstacles and crates. As the bombs spawn, however, the pressure mounts - the map is designed for several bombs at once, although even a single bomb can be challenging since the defenders start off in a last stand position with attackers spawning right on their doorstep as well as at the bomb spawn/s. It comes down to tactics - the defenders are stuck defending, they don't get a chance to go sapping the bomb or spawncamping the attackers, but they're able to put up one hell of a fight from the start so the Blues need to really work together to drive a wedge into one of the few "weakpoints" (the weakest one being the front door, weakpoint is a relative term in this map... :P)

feel free to take my experiment for any occupation maps you make - I think you might enjoy the change of pace, and it has an intense "ready or not, here we come" vibe which I think will mesh well into your map series

Oh, I DO like that! Yeah, I'll definitely check that one out once I'm back on my feet! Thanks!!