Could someone let me know if it is possible to use rigid_model files for the campaign map from Napoleon in Empire TW?

My aim is to make a mod for Empire that adds a bunch of new unique buildings for factions, and I want to use the models from Napoleon.

https://www.twcenter.net/forums/showthread.php?651483

https://www.twcenter.net/forums/showthread.php?594156

I have used these 2 tutorials for guidance, but I must be missing something...

So far, I can't get the artpiece to show up in the dropdown menu under buildings_faction_variants.

To troubleshoot, I also tried naming the import file from Napoleon with a rigid_model name that already exists and replacing the original. By doing this, the model showed up on campaign map after the building was built, but it was all black. I assume that's no texture?

I'm using Pack File Manager 5.2.4.

Would appreciate a step-by-step guide from someone who knows if and how this can be done.

Thanks!