I think Y_Y was trying to convey that PIN expands to Personal Identification Number, which does not apply if no specific person can be identified.
In any case, your proposal suffers from the flaw that in a real emergency, nobody will have the extra seconds to spare to look up a code, because that would literally be thousands of people dying per lost second, so the emergency codes will all rotate from '99999' through '99999'. And an employee would actually be responsible for changing the codes from '99999' to '99999' every time they are required to rotate.
In any case, your proposal suffers from the flaw that in a real emergency, nobody will have the extra seconds to spare to look up a code, because that would literally be thousands of people dying per lost second, so the emergency codes will all rotate from '99999' through '99999'. And an employee would actually be responsible for changing the codes from '99999' to '99999' every time they are required to rotate.