Up until now (and this is still how things currently are):
You had layouts, ABF, Buu, Industrial, etc. That defined their own functions on where placement was, how options were displayed, etc.
One real layout is left: ABF, which will be henceforth called "Meta-layout". This will then be hidden from the user as it is assumed. A new layout system will be built on top of Meta-layout, where you can choose what kind of settings you want to go with, e.g. Buu-style with portrait on top and such and icons on the portrait maybe, or ABF-style with portrait on left and icons in the corners, or oUF-style with portrait on the left and icons somewhere else.
Whenever you change a setting, a new "Custom" layout is created, which can be saved and given a name. There will be an export function so that you will be able to post on the forums layouts you made (this is what I'd like to see most). There will also be an easy way to import layouts. I might even theoretically allow for you to export a layout to your guild and have them import it into their database automatically.