"Scene unit" material node

It'd be nice to have a material node that can be used to automatically scale a material to repeat at, say, 5 cm, no matter whether one Blender unit is currently a meter, or a millimeter.

I'm asking for a node where you fill in a measurement in the unit of your choice (number entry + unit dropdown, E.G.: "5 cm") and it has a single number output that gives you that amount in Blender Units. A fallback option, if no unit system is used ("None" as a unit system), would also be nice.

When combined with unit-scale generated textures as suggested in blender.community/c/rightclickselect/yMgbbc/ , this should allow procedural textures to be easily applied to objects regardless of their scale or mesh, and achieve a consistent feature size. This would help in building a library of procedural materials.