Maybe make it all under one text event, and add a flood pro to the !now an !next trigger so others don't flood the room with it.
Been awhile in coding msl but maybe something like this..
Example:

on $*:TEXT:/^!(setn(ow|ext))\s(.+)|^!(now|next)/iS:#:{ 
  if ($regml(3)) {
    if ($nick = $remove(#,$chr(35))) {
      set $+(%,$iif($regml(1) = setnow,now,next),.,#) $regml(3) 
      msg # $iif($regml(1) = setnow,now,next) playing set to: $regml(3) 
    }
    else { msg # You can't do that. You aren't allowed. }
  }
  if ($istok(now|next,$regml(1),124) && !%f) { inc -u5 %f
    msg # $($+(%,$regml(1),.,#),2)
  } 
}