It's now 2018. Are there any shortcut configuration changes I've missed?
For me it seem that there aren't any changes so far. In my opinion pressing two mouse buttons for this setting doesn't make sens. Especially when your using a tablet.
Other Softwares (Krita, Photoshop, Sketchbook) have much better solutions for brush size and hardness. It's a lot of inspiration out there to make this more useable.
For me as developer, to change this doesn't seem to be very difficult from a programmer's point of view.