Here's an idea:
Code:

[color:#840017]
;  If you're not opped, this script will not fire; you couldn't possibly do anything about it if
;  you weren't opped in that channel, so why bother looking?
;  [/color]
on ^@*:JOIN:#:{

  [color:#840017]
  ;  If the userid:
  ;  · starts with a ~
  ;  · is all lower-case alphabetical characters only
  ;  · 8 or 9 characters after the ~
  ;  [/color]
  if ($regex($address, /^(~[a-z]{8,9})@.*$/)) {

    [color:#840017]
    ;  Then reformat the join line to reflect a possible drone join
    ;  [color:#2B5932]* [color:#FF0000][Possible Drone][/color] Joins: Nickname ([color:#FF0000]~abwgohety[/color]@12-34-56-78.host.com)[/color]
    ;  [/color]
    echo $color(join) -it $chan * $+($chr(3),$color(ctcp),[Possible Drone],$chr(3)) $&
      Joins: $nick $+($chr(40),$chr(3),$color(ctcp),$regml(1),$chr(3),@,$site,$chr(41))
    haltdef

    [color:#840017]
    ;  Add their nick to the channel's entry in PossibleDrones.ini to be removed by their
    ;  departure from the channel or by their response to the CTCP VERSION sent them in the next
    ;  step. Using the ctime as the value allows you to check later how long it's been since you
    ;  asked for their version reply (in effect, pinging and VERSIONing at the same time).
    ;  [/color]
    writeini PossibleDrones.ini $chan $nick $ctime

    [color:#840017]
    ;  Quietly send them a CTCP VERSION, which is blocked on clients only by ignoring all CTCPs 
    ;  and slightly less likely to be scripted in on drones.
    ;  [/color]
    .ctcp $nick VERSION
  }
}
  [color:#840017]
;  Now we'll need something to capture the VERSION reply, if there is any.
;  [/color]
on *:CTCPREPLY:VERSION*:{

  [color:#840017]
  ;  %i will be the loop index through $chan(), if necessary.
  ;  %ctime will be used to calculate their ping time from the value stored in the ini file.
  ;  [/color]
  var %i = 1, %ctime = $ctime

  [color:#840017]
  ;  If the userid matches a possible drone, then check each channel and echo out the All-Clear
  ;  for this user.
  ;  [/color]
  if $regex($address, /^(~[a-z]{8,9})@.*$/) {

    [color:#840017]
    ;  Check each channel
    ;  [/color]
    while $chan(%i) {

      [color:#840017]
      ;  Store the current channel in a variable since it will be used past another if statement
      ;  and therefore $ifmatch will be overwritten with a new value.
      ;  [/color]
      var %chan = $ifmatch

      [color:#840017]
      ;  If there is a value stored for this $nick for this %chan, retrieve it
      ;  [/color]
      if ($readini(PossibleDrones.ini, %chan, $nick)) {

        [color:#840017]
        ;  Echo out their ping and version reply
        ;  [/color]
        echo $color(info2) -it %chan * Possible drone $&
          replied in $duration($calc(%ctime - $ifmatch)) «» $2-

        [color:#840017]
        ;  Remove this entry from the ini file.
        ;  [/color]
        .remini PossibleDrones.ini %chan $nick
      }

      [color:#840017]
      ;  Go to the next channel.
      ;  [/color]
      inc %i
    }
  }
}
 [color:#840017]
;  Script self-cleanup
;
;  For every non-me user leaving the channel, either through part, kick or quit:
;  [/color]
on !*:PART:#:{
  [color:#840017]
  ;  If this user matches a possible drone...
  ;  [/color]
  if ($regex($address, /^(~[a-z]{8,9})@.*$/)) {

    [color:#840017]
    ;  Remove their channel/nick entry from the ini file.
    ;  [/color]
    .remini PossibleDrones.ini $chan $nick
  }
}
on !*:KICK:#:{
   [color:#840017]
  ;  If this user matches a possible drone...
  ;  [/color]
  if ($regex($address, /^(~[a-z]{8,9})@.*$/)) {

    [color:#840017]
    ;  Remove their channel/nick entry from the ini file.
    ;  [/color]
    .remini PossibleDrones.ini $chan $nick
  }
}
on !*:QUIT:{

  [color:#840017]
  ;  If this user does not match a possible drone, then stop processing.
  ;  [/color]
  if (!$regex($address, /^(~[a-z]{8,9})@.*$/)) halt

  [color:#840017]
  ;  Otherwise, %i will be the loop index for the common channels.
  ;  [/color]
  var %i = 1

  [color:#840017]
  ;  For each channel you share,
  ;  [/color]
  while $comchan(%i,$nick) {

    [color:#840017]
    ;  Try to remove their entry, whether present or not.
    ;  [/color]
    .remini PossibleDrones.ini $ifmatch $nick

    [color:#840017]
    ;  Go to the next channel.
    ;  [/color]
    inc %i
  }
}

 [color:#840017]
;  If you deop yourself, remove the entries for that channel from the ini file.
;  [/color]
on me:*:DEOP:#: if ($opnick == $me) remini PossibleDrones.ini $chan

 [color:#840017]
;  If you part a channel, remove the entries for that channel from the ini file.
;  [/color]
on me:*:PART:#: remini PossibleDrones.ini $chan

 [color:#840017]
;  If you exit mIRC, remove the entire ini file.
;  [/color]
on *:EXIT: .remove PossibleDrones.ini

Just some thoughts I had in passing how it might be done. You could do much the same thing using a hash table entry using something like network•nick = $ctime #chan1 #chan2 #chan3 to make it multi-network aware, though most likely with drones, it won't matter regardless. Most of their nicks and the channels they go to won't repeat anywhere anyway.

DALnet: #HelpDesk and #m[color:#FF0000]IR[color:#EEEE00]C