I was talking about rendering groups of bsdfs, have them write to (an) intermediate buffer(s) then combining them later on with a final pass. But you're right, it'd take too much time to just develop let alone maintaining.

Following up, maybe we can branch off and have EEVEE render such materials by doing multiple passes? I may be able to work on this but I'm a rusty in OpenGL and I don't have much knowledge of the Blender's code base.

Yep, it's not about the version itself as the specification doesn't include a max limit. In fact 16 is the minimum that specification allows, funny eh?

Ok, here are the results:

The file you attached doesn't work on my machine. I'm going to try the --debug-gpu argument and post the news.

Here's the .blend file. The issue may not have anything to do with normal maps. I think the problem rather has something to do with the number of textures or the texture memory required. Please note that the actual textures are not packed into the blender file because it would take forever to upload it with the textures. Also, one more thing, when I used procedural textures instead of image textures, the bug didn't seem to occur.