Could I request a "retell" command as well? Basically, after whispering someone you could do "/retell <nick>" and it would whisper the previous message to <nick>. This would be useful if you whispered the wrong person, or if you want to whisper the same message to multiple people. Actually, maybe you could even have "/retell <nick>,<nick>,<nick>"? Anyway, nice work, cheers!
Isn't that basically what happens if you just scroll up to the last thing you sent and put "/t (corrected nick)" in front? :p If anything that sounds more like it'd be tell forwarding than re-telling.
Another request for if/when you get the ones you currently have planned squared away -- you've got tell target already, so how about a target [the last person who sent you a] tell? It's more for convenience in buffing someone who whispered you than of any real use.