I remember either MrFibble or MasonFace said he will implement his spriter into the unity.
T'was I! (https://forums.dfworkshop.net/viewtopic.php?f=22&t=1613
) I've already got a prototype for Spriter weapons in Unity, but not in Daggerfall Unity; been distracted by all the AI upscaling, and... you know, having a baby and stuff. And work too, I guess.
As far as voxels, I don't think Unity supports voxels, except maybe those that have been converted to polygons with like a marching cube algorithm, but I could be wrong. Although Unity does support something called a 3D texture, but I think that's something else entirely. Since you mentioned voxels, I think you'll like the fact that Spriter is configurable so that you can change the resolution on-the-fly to get all the jaggy, luscious pixelness you want, or as sharp and you want. Same with the frames per second.
I would simply say that if you were to create weapon models and animations, I have no doubt that they will get used eventually. I've been petitioning artists to share a weapon model with me so I can do some testing, but I haven't heard anything back from megaten (check his work: https://forums.dfworkshop.net/viewtopic.php?f=14&t=1612
) and VMBlast's hard disk failed and he lost the models he was working on. I'm too embarrassed to showcase my latest Spriter demo with my crappy war hammer made out of box and cylinder primitives...
Now, to get to the crux of your question:
If I had to guess, support for replacing 2D weapons with 3D ones won't be considered until after DFU version 1.0. Until then, you can bake your models and animations into sprites like what megaten is doing. Just make sure you keep you models and animations backed up and safe until full 3D weapons are implemented in DFU!
If I've learned anything from working in this community, it's that if you'd like to see something done, just jump in and get started! It's a very friendly and helpful community. We're all just here to play the best version of Daggerfall that can be created, and in that spirit, it's in all of our best interests to help each other out.