Occluded Geometry Selection Overlay

The problem:

Currently there is no way to tell if you have selected something on a hidden/occluded part of the mesh when working with Solid Shading or Material Preview/Render mode.

Obviously to see through our mesh we need to use X-Ray mode, but therein lies the problem:
X-Ray mode is often messy and lacks visual clarity when working with denser meshes, making it hard to actually see what's going on at a glance.

The solution:

Introduce a new overlay option to show selected occluded geometry.
This would solve the need to check selections with X-Ray and keep the readability of Solid Shading, while also solving the incompatibility of Material Preview and Render mode viewport with X-Ray.
Here's a proof of concept demo created through a crude script:

The overlay should appear more transparent and desaturated compared to regular selections to help distinguish what's what.

Bonus Suggestion to go along with this overlay proposal:
Allow selection tools to customize front face and back face selection options individually in the keymap options. This would allow users to customize the behavior of selection with modifier keys, for example: Holding ALT while dragging a selection would select only backfaces, and SHIFT + ALT would deselect only back faces, or the same setup could work on both front faces and back faces, without having to enter X-Ray mode.