This shaderpack is very beautiful considering it competes with Enhanced Default shaders FPS-wise; the only thing I find missing, though, is normal map & PBR support. It's something that adds a touch of life to the game while also being something that could be toggled off for extra performance.
Unless adding PBR and normal map support would mess with/wouldn't work due to optimization, I would really like the feature added to the already amazing shaderpack.

You have hit the nail. The shader would have to change to incorporate PBR, making the code somewhat unmanageable if we want the current performance when disabled.

I also think it would affect performance more than people realize.

I don't have much time to do it either. I'm afraid it's not planned to add new features indefinitely, except support for new versions of Minecraft, if something is added that needs attention.

Yeah, I figured it would be something about the heavy optimization used in the shaders, normal maps and stuff probably wouldn't be compatible with and would mess up the optimizations used in the shaders. The rest of the visuals are great for the performance so it's honestly not much of an issue lol.