4 bars on the bottom and 1 on each side would be great. I also like to organize my bars based on what the effects or abilities are. This does tend to leave 1/3 or so of my buttons empty but I feel better organized.
I know you can scroll through additional bars so we do have more available for us to use but this is not the same nor does it feel very efficient.
On the programming side of things, this cannot be a hard thing to add after the UI changes go into effect.