If anyone is interested in this script, here is the final product that works as well as I think is necessary. I may have missed something, however.
Code:
on *:TEXT:*:?: {
  .timer $+ $server $+ $nick 1 300 echo 7 -a Don't forget about $nick $+ !
  .set %rem. $+ $nick 1
}
on *:ACTION:*:?: {
  .timer $+ $server $+ $nick 1 300 echo 7 -a Don't forget about $nick $+ !
  .set %rem. $+ $nick 1
}
on *:NICK: {
  if ($($+(%,rem.,$nick),2) == 1) {
    .timer $+ $server $+ $nick off
    .timer $+ $server $+ $newnick 1 300 echo 7 -a Don't forget about $newnick $+ !
  }
}
on *:INPUT:?: {
  .timer $+ $server $+ $active off
  .set %rem. $+ $active 0
}