As I have a lot of performance problem with my 400k Collection I thought a good thing would be to split roon core in different peaces.
One Machine for management GUI and DB, another Machine only for do the streaming part with the DSP
Think of the planet and archive what you haven’t listened to in the last two years . I’m sure that would reduce your library enough not to do this. 
I did suggest this a while back for big collections, mostly for the management of the collection. I remember it got a firm no at the time! However your idea is the principle on which HQPlayer works. Roon for all the library management stuff and HQPlayer on another machine for DSP and playback.