Currently, armor trims only support emissives if used with the "default" minecraft armor trim system. However, there is an alternative way to utilize armor trims to apply entire skins/textures onto armor by making each "skin" as a new trim pattern, and this format doesn't appear to support emissive textures. If needed, I can send an example data/resource pack that shows an example implementation of this system.
Currently, armor trims only support emissives if used with the "default" minecraft armor trim system. However, there is an alternative way to utilize armor trims to apply entire skins/textures onto armor by making each "skin" as a new trim pattern, and this format doesn't appear to support emissive textures. If needed, I can send an example data/resource pack that shows an example implementation of this system.