The Idea is to have a "Custom Property" Node for Cycles to access a Custom Property from the Object the Material is assigned to. So for example, you could have two Objects that both have a Custom Property "mix_fac" with different values.
Optional functionalities could be:
* **Fallback Input:** This will be used if the Object has no Property with that name or if it's NaN.
* **Color/Vector Values:** If the Property is formatted like "128 128 128" or "0.5 0.5 0.5" for example for middle grey, it will output a color/vector
* Alternatively the existing Attribute Node could be used for this instead of a new Node.
A System like this could be useful for example if you have a small Group of trees and you want individual control for the color without creating a new Material for each one. Or you want a different Noise scale for each object etc.
Also this would make it easier to develop addons for Cycles, since Custom Properties can be changed very easy.
PS: I know there are ways to do most of this with Nodegroups etc. thats not the point.