I'm working almost exclusively with the Pixelprocessor and FX-Map Nodes in Designer, because these Nodes are fantastic to create custom tools and effects. But lately I'm touching the limits of both Nodes very frequently. I try to find workaraounds and hacks, which is fun but it brought up the idea of this feature in Designer.
The Scripting - Node
Let's call it Scripting Processor which actually allows the user to load a script and the Node compiles this into a "Pixelprocessor" or "Shader" like Node.
Blender has a similar Node for the Shader Editor (Open Shading Language - Blender 4.3 Manual) which is fantastic, for shaders. In Substance Designer it should have more the behaviour of a Pixelprocessor, but instead of the Substance Function Input (which is unfortunately sometimes very limited, when it comes to complex functions) it could load a scripting file, which allows the user to create very complex nodes.
It doesn't have to OSL it also can be GLSL or even python or lua or any other scripting language, which is easy to learn and open source.
Thank you
Stay healthy and creative Marco