Actually, a level might have some additional value if mounted in a straight-edge, as it could be duct taped in place to fix a broken seat...or use with chewing gum affixed to one end to retrieve a contact lens dropped down a storm grate in the ramp.
Or maybe used to level an RV.
I dont believe I've ever seen a NTSB recommendation to tape a level from an aitomotive recreational vehicle to the instrument panel to help prevent spatial disorientation. I'd like a reference to that report.