In blender you can paint a texture to a mesh with vertex painting mode, and then export the .ski
If it was originally a npc type .ski you will need to then copy and paste the model data chunk into a working weapon .ski or:
another better way to do this would be to save this ski, open a existing blade .ski that works and loads with your plugin, then add this .ski into the scene, mimic the vertex group names of the original blade onto the new blade you added into the scene, then delete the old blade mesh, link new texture, if its not mapped right then use vertex paint mode in blender to map the texture to the unwrapped model and then save and then u want to open 010 editor with a ski.bt structure file and compare parameters before and after to see if any ski mode types and version numbers or any dumb poop got corrupted when exporting, then test ingame, most likely the model will show up but it wont be in the correct 3d orientation in 3D Space, so you look ingame and look in blender and rotate + move the model where it needs to go, and then eventually you will have a working blade model.
If you are unfamiliar where to find the buttons to link a .dds to a mesh in Blender of that version just google manuals or tutorial videos for basic blender UI and find it. Its a very annoying software to use.