There is the -n switch and a check box in the favorites (when adding/editing an entry) which causes the channels to open in minimized mode. When you see the channel you want to type in open inthe switch or toolbar, click the channel and it will become un-minimized and you can type your message(s) while the rest continue to open in minimized mode.
While this doesn't 100% cover your request, it's a currently available option.