From the security point of view, no. Not the check for a username - as everyone can switch to that unregistered name.
Registered nicknames and network services will prevent possible abuse, and even there you have the potential of insecure passwords and the like.
If you want to incorporate it anyway, look up "if then else conditions" and "on notice" in the helpfile.

Sidenote: While it's questionable to entrust op rights to a person that is either unable or too lazy to register its nickname, the automation of that process, opening a huge abuse vector, sounds asinine to me.