No need to implent a server system within mIRC's program
I think it wouldn't be that hard to use the same debug system and make mIRC thinks it comes from the server.
instead of having the server sends us stuff having a new identifier to know if it's simulated or not with the debug window.
@debug window would looks like that.
<-

arkRift!~dark@holyrift.users.undernet.org JOIN #mircscripting
<- :mesa.az.us.undernet.org 366 DarkRift #mircscripting :End of /NAMES list.
-> mesa.az.us.undernet.org MODE #mircscripting
that's for the normal server reply
simulated could be like this, replacing the adding SIMULATION after the servername
$simulate would return $true here
<- SIMULATION

arkRift!~dark@holyrift.users.undernet.org JOIN #mircscripting
<- :mesa.az.us.undernet.org SIMULATION 366 DarkRift #mircscripting :End of /NAMES list.
and for out
-> mesa.az.us.undernet.org SIMULATION MODE #mircscripting
but that one would not go to the server of course.
maybe adding a TAB in the options for script system and make a check box "Enable Simulation".
lots of peeps want to have the script system improved anyway that would be a nice feature for it, allonwing to simulate your stuff, just like a debugger for programmers. so no need to piss other guys off to see if it works