Still working on it:
http://img245.imageshack.us/img245/3411/starwolves6.jpg

It is possible to add GKTurrets to Motherships (I mainly did this modification to test that), the problem is that the GUI infestructure is not in place to handle them, this means that you cannot equip or unequip them, so you have to not only spawn the mothership with them already equipped, you cannot swap em around as you need it.

The reason why I picked the Lion in particular is that, the Left/right turret mountings always felt like they were meant for a much larger turret. It seems like the developers may have originally intended the Lion to carry GKTurrets, considering how perfectly they fit.

Now the Lion has 2 GKTurrets, 4 GKGuns, 8 Turrets, and 8 Systems.

1.No
2.Yes
3.Using some dev-tool i think

Is it possible to model for this game? Was thinking someone could mod the Stone Turtle to have a docking ay on it's belly as an astarte replacement (looks wise)

IMDEditor v3 by Tech + 3DMax

Ug. 3DS Max.

Could you describe how to do this?
I'm now trying imd editor but don't know how to find right positions for all these guns.

Guesswork. Pretty much you insert in coordinates that you think is the general vicinity of where whatever it is could be (use the X Y Z picture of the Arba that the IMD editor shows you, it really helps!), than you enter ingame and test it out.

Now I'm trying to activate more than 4 turrets but can't do this. If I try to put turret in the 5th slot I have to remove another. Is this the GUI limit you mentioned?
Is it possible to add GKGun to the ship that not has right place to mount it.
Major Caliber turrets - Did you use those from stationary platforms?

Could you upload IMD file for your fully equipped Lion Cruiser, please?

Can anyone tell me how to add more slots to GUI, because so far nothing i try works. Thanks.

you're right, does look like those mountings were meant for major caliber turrets.