Nice ideas except for this one:
echo -a we never get here, because /error halts.
Often I like to give 'warnings' (the script continues but you get a warning), I don't think /error should halt.
I'd also like to see some kind of error handling on a global scale:
on *:mircerror:*:{
; $error - the error.
; $etype - what caused the error? - alias/commandline/dialog/event/menu
; $script - script the error called from/found in.
; $scriptline - script line number.
}