Any chance the copper hopper texture could be made into its own standalone model? I use Vanilla Tweaks directional hoppers in my resource pack and they conflict with each other and blend the textures. Just a thought.

Wouldn't a blend of the two textures be desired? Can you post a screenshot?

You should be able to also override the copper-hopper model textures in your resource pack:
https://github.com/pcal43/copper-hopper/tree/main/src/main/resources/assets/copperhopper/models/block