Hi Jeroen,
there’s currently no host I know of using this. I once (10 years ago) had a prototype on macOS working, but at that time all non Steinberg VST3 plugins were not able to do this (because they implemented IEditController and IAudioProcessor in the same object, or much worse communicated a pointer address to the other part and used that directly). But with the few plug-ins with a clean separation between controller and processor it worked.
Cheers,
Arne