Well I'd disagree about the 200mm point (and even if it were true its still going to be perception that drives sales) but I think your talking more than just super tele's, even something like the 24-105 would be unbalanced on an M9 sized body for me.
This is another point that the peanut gallery is generally missing.
A small, lightweight camera is pointless without small, lightweight lenses.
And there are some very hard physical restrictions that come into play when designing lenses. The Shorty McForty is about as small and lightweight as a lens that covers the full 135 format image circle is going to get, and just look at all the people bitching because it's only f/2.8. If you want faster-than-f/2 in a normal prime, you're not going to get much smaller and lighter than the Plastic Fantastic. And if you want something that fast and either wider or longer, it's going to get really big and heavy right quick.
So, if you want small and light, you'll either have to go with something slower or that doesn't have as large an image circle. And probably both.
YES. small wide-angle to standard lenses are important. This is EXACTLY why I would love to get a small Canon FF mirrorless body (size like Minolta CLE) with an electrified Leica M mount, call it Canon EM. :-)
You surely know, how really small many of those M-mount fixed focals are? All of them built for 135 image circle. Available all the way to f/0.95 not just f/2.8. I am sure, it is possible to build a 40/1.8 lens for a FF mirrorless cam which is still smaller than the EF 40/2.8 pancake.
Zooms are a bit tougher, but some constant f/4 "kit-zoom", say a Canon "EM" 24-70/f 4.0 IS for FF mirrorless could for sure be quite small. I would even skip manual focusing gear and ring, since i never use it anyways. And 90% of users do neither. And those video guys shall go buy proper Canon camcorders rather than trying to cheapskate on our stills cameras. :-)
Agree, but I would actually forgo AF on most lenses! Never had much value in AF on wide angle or macro lenses - half my kit is MF lenses.