There definitely is room for a 15/16/17-45/50/55mm f2.8-4 in the Canon M lineup. To those that despair that it wouldn't be possible to do with a 61mm diameter, take a look at the Fuji f2.8-4 standard zoom. That lens has a 65mm diameter. And it was never engineered to specifically fit within a certain diameter, so presumably there is room to slim it down a little to fit within the prescribed Canon M diameter. Just look at the Sigma 30mm f1.4 DN and the Fuji 35mm f1.4. Both lenses have a 65mm diameter, and Canon was still able to make their 32mm f1.4 with 61mm diameter.
Also, lets not forget there have been Canon M patents for 15-45mm lenses with apertures f/1.8-3.5, f/2.0-4.0 and f/2.8-5.0.
So in summary, a relatively fast-aperture standard zoom is very possible from an engineering standpoint, it is a glaring omission in their current Canon M linupe, Canon has recently shown with the 32mm f1.4 that they do intent to introduce faster lenses to the lineup, and there have been patent applications for just this type of lens. In my opinion there is a ~80% chance such a lens will be unveiled in the next 2 years.