Visitor role mode as chat command

Hello,

while running a multiplayer MC:EDU class, sometimes a teacher must enforce rules and behaviour response. What we have are chat commands like "/deop" which puts players in the Member role and "/op" to put one into Operator role.

What is missing is a chat command like "/visitor" which puts players in Visitor role. With "@a" the teacher can force the hole class into Visitor mode, and back. This is highly needed, to get full attention of the students to the teacher. Or to set a short pause.