There is a standard - DIN.

Crestron makes it, Lutron makes it for Europe only.

Since the modules have to fit on a DIN rail in a DIN enclosure it requires things to be as small as possible in width and a pre-defined height. This means swapping modules shouldn't be an issue going from one system to another.

Now try and get manufactures to agree, by the time they do we will be using bio-luminescence and have no need for dimming systems.