I'm probably in the minority here, but I think everyone who wants a soup-to-nuts 'yes, we offer that' in mirrorless would be wiser to leave Canon/Nikon immediately. Fuji, Sony and the m43 gang will far, far better support your ambitions. They have multiple mirrorless body price points and all sorts of tiers of tiny/average/big sensors and cheap/okay/semi-pro build qualities. Plus, they have a ton more lenses that are native to the mount than with EF-M.
I also do not understand why folks want reach for these microscopic bodies. I might be way off here, but mirrorless needs to be small. Period. The minute the camera gets above length X with lens attached -- let's say 6-8" -- I think the upside of that tiny body is lost. Sure, it will pack in a bag far more efficiently when you take the lens off -- and I see a lot of folks rave about how small it truly packs down to -- but I always have a lens on my camera, so that awkward 'T-shape' of camera plus lens will still be a pain to deal with. In my mind, Canon should cap mirrorless to a FF equivalent of 85mm perhaps. Otherwise you get something like this (see attached) and I have no idea why on earth you'd do that without the bigger body as a counterweight and grip to properly wield that thing.
I think mirrorless ought to be well served from, say, FF equiv 24mm to about 85mm and stop there. Who wants to hold a pickle jar of a lens with a body as big of a deck of cards?
This also might serve as a way Canon could nerf (make less appealing) the EOS-M in an intelligent way to protect SLR sales. Rather than withhold vitally needed tools (like a viewfinder) or cripple the performance (the AF), just limit the focal length options. Think of this sales pitch instead of what we have now: "EOS-M will give you stellar shots with all the viewfinder comforts and knobs and switches you love and great AF performance, but only from 24-85mm FF equivalent. If you want an ultrawide or a tele, please see our terrific line of EF-S and EF mount cameras."
But if you want Canon/Nikon to evolve all their hardware -- lenses, bodies, flashes, etc. -- into the smaller format, give up now. Won't happen for years and years. Again, consider a company like Sony/Fuji/m43 who is actively trying to build up their mounts with more options. You'll find more joy there.
That's what I did...I have two MFT cameras that complement my 5DIII.
I have two "full" kits...and let me say that my MFT kit is more than adequate for a LOT of my photography. It is high quality and a pleasure to use. It is too bad that Canon does not pursue this wonderful compact solution to photography in any really meaningful way. They could lead the pack. "To me" the M is not much of a camera.
..but I know that everyone does not feel that way..and that's ok.