This is probably better-suited for the valet thread, but I think we need to understand why the valet takes a joy ride... is it to "open it up" and play with the awesome power? Or is it to show off? Or some other reason.
Tesla has said valet mode limits power and top speed, along with removing places and locking the frunk/glovebox. We know it limits speed to 70 mph, although I haven't seen the power restriction. Let's say they limit it to 80-100 kW.
Would that be enough to deter the joyrider, if the car acted like a mid-range Chevy when they tried "hammering it"?
What if Tesla added a valet summary as it asked for the valet code to disable valet mode? Something like "Valet mode entered DD-MMM-YR HH:MM:SS, odo 10304 / elapsed time HH:MM:SS / total miles driven XXX.X". That would give you at-a-glance stats to see if something were up.
If I saw that remote access were disabled, I'd be calling for the manager immediately. Personally I'd like to see all settings locked.