+1 to pack animation and footprint issue (Though I would be content with increasing the DDM's footprint, anyone else?).
If you had the gun rotate upwards and then the circular piece below it lower with the whole turret, with the done closing behind it, that would work well and would not even require any texture changes, just creating a cylindrical 'lift' section for it to go down the middle.
I worry also that the texture is going to be too noisy or dark from a distance, that you'll lose any detail and it will appear grey. This is, of course, a problem with basically everything in Spring if you put a lot of detail on it. We'll see how it looks ingame though and with teamcolour.
You've also got a bit of texture stretching on the dome there, the 'screw' pieces. I know that can be hard to avoid when using circular pieces but it should be able to be solved.
Finally, when the gun is pointing downwards, towards it's base, it may clip into the metal side struts.