From my POV the "Viewer" property is to link the measurement units to applications like SSVC.
I think adding units to xProperties is possible and I like the idea, but it requires a lot of effort. You probably need to customize the xClass app on codetree and database level. First I would try to find the code that is used to "store" a specific xProperty value inside the database. Next the rendering for the Form element. Please keep in mind that we have the classic and new Form editor....
How about a more trivial solution like this: Just write the unit next to the label?
