If anyone else stumbles upon this thread, my missing texture issue turned out to be caused by incorrectly selecting the "Game Data Path" in the Bodyslide settings (the ones that you access by launching the .exe) due to installing Skyrim in a non-standard location. Since Bodyslide couldn't find the Skyrim install when I first launched it, I had to manually locate the install folder and selected "\SteamLibrary\steamapps\common\Skyrim Special Edition\". However, that was a mistake; it turns out you have to select the data folder, which has a path of "\SteamLibrary\steamapps\common\Skyrim Special Edition\data\". When the wrong path was used, it created a new meshes folder in the Skyrim directory instead of in the data folder. After fixing that, textures loaded and I was able to build outfits. Hope this helps.
Perfect fix for the same issue, thanks!