Detecting how much of a Sphere is overlapped

I'm currently working on a system which requires an "Overlap Sphere" cast to detect how much of the sphere is filled by an object. As an example, I may have 3 objects within the sphere; the ground, a wall and the player.

I ignore the player with a layermask, and attempt to detect the other two. I want to know whether there is more floor or more wall within the cast as I intend to use this data later.

If there is no way of using the "Overlap Sphere" cast for this, alternative suggestions would be appreciated.