But that's a terrible idea! It means you get the ugliness that OSX has writ large; input focus is half floating and half click to focus. Which means you'll be happily typing in something and then hit a menu shortcut, and the shortcut goes to some other program entirely that you forgot you left menu focus with.
That happens to me in OSX all the time. I'm on irc, one of my colleagues sends an url. I click on it, it opens in firefox. I use the scroll wheel to scroll through the article, then hit clover-w (close window/tab).
I've just killed my irc session, because while scroll focus was floating over the firefox window, the menu focus was still on the last thing I actually clicked on, which was the irc window.
I still get bitten by that several times a day, and I've been on osx essentially full-time since november.