So here's just the perspective distortion. The rest should be pretty straightforward to add

I'm not sure what you mean, seems to be working fine, no?

"If texture_2d allowed vector4 instead of a specific texture input"

A Vector4 Doing what, exactly? Texture distortion is done using UV coordinates, and they are *always* Vector2s, unless you're using 3D textures.

I'm sure it's possible by just altering UV coordinates in a chain.

Just use the UV input. UV coordinates are always only two components for texture mapping. What you'll want to do is to first rotate UV coords using the UV coordinate node and the Rotator node, then use the add node to add a distorsion texture to it, and then plug it into the UV input of the Texture 2D node

Oh, hm, strange. I have no idea why that would happen

Right, this is something I've considered doing, but haven't because nobody has requested it before. I do have a reason now though :)

Removing d3d11_9x should have the same effect as checking DX11 for windows RT in the shader render settings, although people are still having issues with it.

If it has 9 inputs, I would presume it has too many interpolators, which could mean the shader you tested was simply too expensive.

Heavily appreciate the writeups here anyhow - I'm unable to test any of this myself

I'm pretty sure I'm using semantics on all variables passed through though, strange

Not even a vector 3 into emission

Does it work when you check OpenGL ES?
Do simple colors work?