Maybe someone should implement a PAM module or something that requires authenticating as two different users with sudo privileges, so you can implement this for as many users as you like and let them each have a single password, instead of half of a password for each possible pair of users.
Use something with 2FA like e.g. https://duo.com/docs/duounix and give person A the password and person B the 2nd factor (phone with this Duo profile configured or whatever).
