I have tried and tried to get this to work yet I seemingly have come to the end of my knowledge and search. How would it be possible to do the following:

I go to a building or unit named "Shop1"
A dialogue comes up displaying multiple "turrets" theyre selling for my ship (I know the dialogue part)
When I click on Button "AutoTurret" the credits are deducted and a building-like interface comes on where I can select where I want the turret to be placed.. But, it cant be placed outside my battlecruiser.
Then when i place the turret in the proper position it appears on the battlecruiser and moves with it.
However, I dont want the ability to stack turrets on top of eachother.
Thus when I was done the battlecruiser would look like this:

Red being the Autoturrets and Blue being another type of turret.

To create turrets for units seems to take a lot of work (For instance, in recreating the Uberlisk, you need 2 Movers, about 30 Actors, about 10 Effects, 5 Units, and a few odds and ends. And that's for 5 turrets.), at least through the data editor. You could expect to spend about 2+ hours in the data editor, and even more coding the triggers. (Granted, tentacle-based turrets take a lot more work than say, regular gun turrets, but still.)

However, in looking for help on that, I did find this: http://sc2mod.com/board/index.php?page=Thread&threadID=89

It explains how to mount units onto other units via triggers (which are not actually mounted, they just move with the unit), and requires hardly any in depth work in the data editor, and should be alot more manageable and easier to code than the previous method. It should also be easier to toggle, as you can create a trigger that just checks to see if they have bought the certain turret, if they have, prevent them from buying it again and attach the turret to the unit).

Wait, I'm not too familiar with SCII, but isn't there a feature that allows one unit to "carry" another unit? Can that be applied to have one unit carry multiple subunits, and can the placing of the carried units be determined?