Well, for me, I just don't use the middle "button" for anything. I scroll with the wheel, but don't use to to click anything. I also don't use the fourth button on my mouse. I just don't need them. And I've gotten so used to just shift clicking the switchbar on whatever I want to close in mIRC that I wouldn't care about having another way of doing it. Considering my keyboard's always close, hitting shift at the same time as clicking doesn't take any extra time than a middle click.
Now, that's just where I stand. I don't mind if something like this is added. I just have no use for it, which is why I never replied before.