Best practise to control render settings on linked files consisting of multiple objects

Lets say I have e.g. a robot that consists of multiple objects that I linked into a scene.
How do I control the subdivision levels (render and preferably viewport) on linked in files that consist of multiple objects?

In 2.7 I used an armature, bound all objects to it, and drove the subd levels through a driver attached to the armature. It was a workaround at least.

All objects created in such a way wont load the driver in 2.8 anymore. When I link the .blend and execute make proxy it literally does nothing on 2.7 files.

1.) How do I get my renderlevels back in 2.8?
2.) Is there a better way to control it? It is a pretty ugly workaround for such basic functionality in my opinion.