I that case change my request to remove the reflections for mirrors at all in the medium setting. Reflecting the surrounding in a mirror inside a building is much worse then reflecting nothing!
No good idea, since the medium setting allow to get light into closed spaced from the environment and this effect helps a lot for lighting closed spaces. So, not all users want to skip mirror reflections at medium settings.
One slider for different parameters is a bad idea and it doesn't help to pack more parameters in this slider.