New Nether Update mobs can't have unique Spawn Eggs

With new mobs added in each update trying to tell the spawn eggs apart by re-coloring the same egg texture becomes increasingly problematic.  Texture pack have been able to retexture each egg to be more visibly distinct (see example below), but none of the new mobs introduced in 1.16 support that.  They instead all use items/egg_mask.png, and cannot be individually altered by the texture pack artist.

Individual .PNGs for each spawn egg is a useful feature and should not be discontinued.