I saw a general version of this feature in another thread ; camera culling it also had the option to add back parts within a distance to get reflections better. It might have been cycles specific though. I’ll see if I can find the link when I get home.
edit: It is already in master. In scene settings below simplify you have use camera culling and use distance culling. You can read about them in the big cycles thread (“brecht’s easter egg surprise - modernising shading and rendering”), page 813.
If you compare them, does your version save memory even for viewport work? Is there a performance cost or improvement? (I’d assume it to be about the same result for rendering?)