This one shouldn't be too hard. Needs CRPL and somewhere you can have space to set up. I'm working on a CW2 map of the same style, just wait until the gateways get to you, then you can get what you need to obtain. Only in CW3, you need to defend your CNs, which once are deployed, cannot be moved or returned to orbit. Victory is obtained when certain circumstances is obtained, the main one being once the percent reaches 100%.
I don't really get your concept.
What you propose here seems to be a step back to the roots of the genre - that is nothing but basic tower defense (enemies come in waves, you have to repel them, you have to survive).
Don't get me wrong, it's not always bad to abandon innovative features (that are for instance: expansion, strategic maneuvers, obtaining PZs) and go back to the origins, but then you have to design it very carefully. Otherwise it will be a Creeper World -1...
... anyways, if you need a script that will do this effect, feel free to contact me.