New Palette Permutations don't allow compat between packs.

The new palette permutation system is a great feature, but it has one major flaw, especially in relation to trims.

As it seems currently, it is not possible for one Datapack to add a new trim, while another adds a new material, without both packs being incompatible with each other. Or well, at least when we get to the resource pack side of things.

You need to specify the input textures and palettes in advance, meaning that you're 100% of the time forced to create a compatibility resource pack. My suggestion for this would be a tag like system for this.
Simply add the textures to tag a, and palettes to tag b.

There will still be a chance that packs aren't compatible because they expanded the palettes, but at least they aren't incompatible out of the box by design.