I finally designed, received and painted an Ursus claw for my proteus pattern warhounds. I tried to take inspiration from my previous research. This is a non-symetrical design, but a simple mirror on the STL would do the trick for a right arm version. The chain was a bit tricky, but the result is not so bad (considering my painting).

I have designed a version that should work with the Mars pattern warhound kit. I have NOT test-printed it, you can see it below, compared to the proteus patern.

And finally, I have printed an arm that allows to mount the inferno cannon on the proteus pattern warhounds (or any other horizontal weapon).

If you want them, you will have to wait until I upload the files find them there: