The Canon 40mm f/2.8 is exactly the kind of lens Sony should make for the FE series, but never will. It's the kind of lens only 'mature' camera systems like Canon make, It's light, small, cheap and seriously sharp, something Sony have so far failed to combine in one lens.
Below is an interesting example of Sony's woeful attempt to 'appear professional'.
Personally I really have no idea as to where Sony are going with FE. The A7r II produces superb stills and video, that's indisputable, but it's badly designed, has build quality that doesn't justify it's price, appalling battery life and has a lens range that's either expensive or mediocre quality and in some cases both. It's no accident that there is a whole industry dedicated to making adapters that allow the use of other lenses on their cameras. I had great hopes for Sony a few years ago, but they are becoming one of the most frustrating of companies. It's like they have all these technical innovators working for them but when it comes to providing tools for professionals, somehow their heart isn't in it, despite them saying again and again that they want to compete with Nikon and Canon.
And if they had done it right, then they would / should have made a serious dent in the Pro market by now. In terms of the quality of results that come out of the A7r II, neither Nikon or Canon have any package that comes close to producing what that Sony camera can, but they house all this in a compromised, incomplete, enthusiast package. That very quality makes many of us put up with the flaws, but Matt Granger and I aren't the only ones who are very ambivalent about what Sony FE offers working photographers who expect a certain standard from their cameras. At least Fuji, Olympus and Panasonic don't pretend that they are Canikon competitors and when we use their cameras we understand that. Sony talk the talk, it's about time they walked the walk.