I've read it. I won't comment on this anymore after this: There is no self imposed "size restriction". There is a market restriction being imposed by the market. This has become a circular argument.
I get that you don't like the Canon M offerings. You are obviously not the target market.
Sigh, just when I thought we were converging on an understanding, you go back to square one.
Indeed it has become circular, because you've utterly failed to explain how the market could cause Canon to decide "all of these lenses must be the same diameter." It's a marketing restriction. Why? Because it's a marketing restriction. Yep, that's a tight circular argument, assuming what it sets out to prove.
The market certainly could explain why the lenses are in no danger of outperforming L lenses (they're aimed at a "lower" market), and why there aren't that many of them (resources must be directed towards RF which will be more profitable).
But "they've got to all be the same OD" smacks to me of an arbitrary decision by someone. I'd hate to be one of their engineers tasked with creating a zoom lens, and having to limit the aperture (or zoom range, or both) because someone up the chain won't let him make the lens 5 or even 2 mm wider--which would still be a pretty darned small lens.
I <I>don't</I> hate the lenses, by the way (but others have complained about their limitations). I just bought a 32mm, have one on order (the 22mm pancake) and another one (11-22) is out of stock at my local brick and mortar, but I'll jump on it when available. That will be a great alternative to my much larger 10-24 EF-S lens (from Tamron).
I originally wanted to point out that the EF-M line metaphysically <I>cannot</I> exceed its present capabilities unless Canon is willing to bend on that outside diameter. And to point out that there's no engineering reason for it (as shown by Tamron's 18-200 native EF-M lens, which IS quite a bit wider). In response you've insisted that "marketing" somehow requires it...and have presented no evidence, or even a plausible hypothetical explanation as to why. "Marketing" likely requires that the lenses be lower-end (which is fine; I know they don't have red rings on them), and smaller than EF-S and EF (to say nothing of the huge RF lenses). But that they be of the exact same diameter?