Some quick observations on new site builder
Using Jamroom
It is something I have used in many site builder like systems on WordPress and yes you are correct it adds a lot of overhead to the learning process, but adds a lot of flexibility. (Visual Composer is probably the most popular on the WP side) so maybe one way around this would be (and it's more work for you)
a: have the method you're proposing as default.
b: have a global setting to enable advanced css features which would turn on these areas in the panel/widget settings.
updated by @garymoncrieff: 04/20/15 11:15:23AM