Moin DivingDuck, well I just tested your mod with the stock NSS_Uboat9_RR.* files, and the hydrophone does work. As well as the opening and closing of the hatch.
However; (and this perhaps was to be expected) when you
open the hatch, walk through it to the RadioRoom and look back, you see this:
Like you said, you made all the changes to the Command Room files, so the stock RadioRoom files I used will also show the stock closed hatch. And I see in s3ditor that the hatch object is attached to a lot of other textures and objects..
Well anyway, my hydrophone works, the hatch opens and from the command room everything looks just fine. So it's good enough for me.
And I hope this info will help you somewhat.
Regards