I quite agree.
A system with a couple of hundred admins is going to end up in a mess if there are no rules and common sense is not applied.
IHMO if you cannot undo it don't do it. That would mean strickly taken do not create any users.
I see the primary use for the sandboxers the possiblity to see and experience what is there and how things work.
It is not for proof of customized concepts. Get your own sandbox for that.
If you configure OOTB items then when you are done restore the original configuration. If you don't how can the others have OOTB experience?