Yeah. I'm currently experimenting with .wad files. I'll see if I can make any texture show up on the map. Although I'm definitely expecting to run into compatibility issues between .wad and Hammer.

yeah you would def need to recompile the map and painstakingly replace every material because .wads and the source material systems are completely different ballgames. there are probably tools for mass converting .vmts into .bmps and hammer has an option to replace a texture instance. should take you an evening if you're dedicated

i believe the only way you're going to make that work is by converting EVERY SINGLE material into a .bmp but even then i believe goldsource maps have pointers to the .wads they're using in their header. i imagine the only way you're getting this done is by recompiling the source map for goldsource with custom .wads

Nope, .vpk are a no go.

I'm trying to import Source maps. There are no .wad files. However, I will try importing the .vpk files.

just put all the .wad files from /valve folder into the same folder you put maps in