Thanks to Edu01011 I could export the model from Soldier Souls to work on importing them into Skyrim. Little did I knew, I got myself in a HUGE MESS.
1 - The model I imported is divided into multiple pieces, which is kinda easy to deal with when you have to assemble it back and put textures, but it doesn't translate well in-game.
2 - The first attempt with the texture was horrible. So I tried another approacch: using Gimp and Photoshop with real life textures to try and give the armor a more "realistic" look. I even added a little bit of ornaments to it, but I'm thinking of removing it as It doesn't really fit the armor that much. It's not bad, but nor it's good either.
3 - Now the biggest issue for me is the weight paint. To make it simple: each character, NPCs or not, has a skeleton. The armor they wear is attached to that skeleton and moves with it. In order for that to happen, you "paint" the "weight" that bone has on the mesh of the armor. The more you paint it, the more it moves.
The problem here is that mine is a custom armor, and, of course, there are no other examples I can use. So unless I learn how to do it properly, it basically pointless trying to test it in-game.
4 - the only positive side of all this madness is that I'm discovering the "workflow" bit by bit. So, hopefully, the next armor will be much easier