This is totally tangential, but I wonder why the new whiz bang electronic gruppos still have the rider shifting FD and RD separately. They could instead have a single shift control that works sequentially, shifting the FD and RD as needed to move however many steps up and down the rider commands. When setting up the system, you could input the chainrings and cogs and the control unit could figure out the steps and which cross-chained combos to avoid. With no need to worry about extreme big-big or little-little combinations, the chain and RD cage could be shorter and lighter.
With Di2, step-and-a-half starts to make a little more sense. If you're programming the derailleurs to move a certain amount with each press of the button, why not two cogs or three instead of just one?
Once somebody figures out how to hack this system, I foresee it becoming a lot more attractive to a lot more people.