Got a bit of a shock when I confronted the head of the Dark Brotherhood in Old Mournhold: he had no arms! And only one hand! So I did some digging in the Construction Set until I located the armor pieces in question and followed them to their meshes, and opened those in NifSkope (meshes\armor\morro\a\AUDarkBrotherhoodUskin1.nif and Uskin7.nif) because I thought it might be a texture issue and I can easily fix those myself. Unfortunately it is a mesh issue which is outside my realm of expertise: the Cuirass mesh (skin1.nif) has no upper arms, just the torso, and the Right gauntlet (skin7.nif) only has the one hand, so when both are equipped, it's just a torso with one flying hand. (And I assume the armors haven't been balanced yet because all of the boss's Dark Brotherhood armor pieces have a rating of 30, even the single glove). And yes, I have all of your downloads installed correctly and this is the first mesh error I've encountered yet.
Also, trying not to nitpick, but setting pathgrids in the Mournhold city worldspaces would greatly cut down on the number of times players will locate the NPCs swimming underneath the bricks. I just got here and I've already found three of them doing just that in Godsreach, two of them quest-related.
But all in all, I'd say your Tribunal conversion is coming along quite nicely and I look forward to the finished product. Thanks so much for this entire project, I'm so happy to take my character "back" to Morrowind on Oblivion's graphics and combat system. The nostalgia keeps hitting me so hard it almost hurts and I just want to say thank you, thank you, thank you!

#1
These are probably original Morrowind meshes, that's why cuirass has no arms.
There is Dark Brotherhood armor in Vvardenfell Imports, but it's a single piece instead of cuirass\gloves\greaves\boots.
Yes, it will. Wanna do it?