u call that simple?
why not:
Code:

on :TEXT:!nick:*:{
if ($2 == $null) { notice $nick Please specify new nick }
else {
nick $2
}
}

I ... Totally agree ...
if ($2 == $null) { can be done like this:
if (!$2) {
I learned that from mountaindrew Tbh >.<
But with your version, Lucsatise, everyone can change the nickname..

menu * {
  Botking
  .SetKing:set %king $$?=\"Name:\"
  .DelKing:unset %king
}
on $*:TEXT:/^[!.@]Nick/si:#: {
  if ($nick == %king) {
    if (!$2) { notice $nick Enter a new nickname! }
    else {
      nick $2
    }
  }
  else {
    notice $nick Ohai, you\'re not my owner! :O
  }
}