Incredibly Complex Procedure follows, disregard if not ready.
Center a location labeled something like ZBase on all Hatcheries, Lairs, Hives, Creep Colonies, Spore Colonies and Sunken Colonies continuously. Make it the size of the finished creep expansion, so it will always cover the entire Zerg base.
Center a location labeled something like ZGateway on all Gateways brought to ZBase contiuously. This will define them as a Zerg base Gateway and stops the "must be preplaced" problem.
That wasn't the incredibly complex part, FYI.
Now you must create 2 mobile grids over each gateway, joy.
Since units are created
(123
456
789)
You should
a) Have a secondary ZGateway location be the size of the Gateway, plus about 3 tiles on each side. Name it something like ZGateway2
b) Have 2 unused computers. (Not exactly necessary, but makes it more professional.)
Create 8 Units owned by the unused computer 1 (Henceforth known as p1) and 1 for unused computer 2. (Same deal) The units should be observers.
You should have something like this.
OOO
OOO
OO
OEach O be an observer, the blue one be the different computers. You don't need the center one so make a kill all observers owned by p1 trigger at ZGateway. Center a new location, named whatever, on the blue O. (Note, it probably won't be blue, nor an O.) Kill all observers. Repeat, this time go 7 p1 and 2 p2. Kill off the one in the old location, and center a new location on the one left. Repeat until you have unique locations surrounding teh Gateway.
Now, do it again. But further out. You should get a Gateway in the middle of a grid, make it so that all DTs brought to the inner squares move to the outer, so you can't unnaturally convert one. Make all the DTs that get to the gateway change into the hero through the standard method. Maybe make shuttles move away too, and overlords. So you can't cheat it.
Now then, do you REALLY wana do all that, or just accept a little glitch?