Hrm. Okay. So, I've downloaded OpenBRF and started trying things...I'll preface this response with another report of failed tutorial and thread diving. All I've seen are things telling me to create a .dds (done) and use OpenBRF without instruction as to how (I'm trying) or how to create a very nice texture (irrelevant for what I'm trying to do).
Regardless, I made a copy of one of the big mesh BRFs that have all of the buttons (core_ui_meshes). I deleted all of them save for one of the longer buttons, which I renamed for my purposes. I then imported a new material with texture and tried to ensure the "flags" number were the same on the material and mesh. My texture shows up with the correct alpha and everything in OpenBRF, so I save this as a new .BRF file--one file including the mesh, material, and texture. I put it in Mod\Resources, add the module.ini line.
Now, no further crashes...but when I try to create an overlay from the mesh, nothing shows up.
A flag problem? Everything can't be in the same .BRF?