Is it, or will it be possible to have “r.Nanite.MaxPixelsPerEdge” option per object?
Lowering this value helps a lot fixing disappearing of small objects in distance such as tree leaves for example.
So in theory it might be good to have tree leaves as separate object with low maxpixelsperedge value to prevent disappearing and rest of scene could use default value.
Some automatic fix would be nice but this could be a way of solving the issue too maybe.