I would like this a lot. I know in other games what I've liked to do is put my faster and more common skills on the main numbered bar, and then use the mouse to activate slower or less common ones. Being able to use keys and the mouse at once makes everything much more efficient for me.

Another suggestion I would like though is to add keyboard binding options for rotating the action bars. As it is, using the arrow keys is horribly clunky, because sometimes the action bar is active and sometimes it isn't. I have, on several occasions, let people die because I hit the arrow key to switch to the bar containing a healing spell but the action bar wasn't active so I switched targets instead. If I could set the rotation to, say, - and =, I would have no issues with this whatsoever.