I think anything other than the pancake 22mm destroys the form advantage of the M.
However, I personally don't want to buy any new lenses that I can't use on my other bodies. EF-m lenses are exclusive to the M. Yeah they might be 30% smaller but it ain't small enough.
And more exclusive lenses are going to backfire, the Ms great selling point to canon eos users is the ability to use your own lenses. A 55-250 is never going to be compact, so lets not kid on otherwise.
Let's face it: Canon has fully botched the EOS-M in every possible way. Even if there were more EF-M lenses NOBODY wants to buy yet another set of APS-C lenses for use on only one camera body, after having purchased EF-S lenses and (possibly) EF lenses already.
Canon should have:
- designed the EF-M as FF-sensored camera-system with a new mount with well thought out diameter and flange distance.
- offer a starting line-up of 2 models: EOS-M-"Pure"= Basic model, as small as possible, LCD only, as cheap as possible
- and EOS-M-"Advanced", slightly larger, possibly somewhat more controls, full weathersealing, Mg-alloy body and hi-end "retina" EFV
- plus starting lineup of 3 native, FF pancake primes, sized like the EF 40/2.8 ... e.g. a 18mm/4.0 landscape, 40/2.8 normal view pancake and ultracompact 85/2.8 portrait lens. All with autuofocus capability only. No manula focus ring. To make 'em really small, fully weathersealed, optically as good as the EF 40/2.8 and as cheap as possible.
- plus one kit-zoom ... similar to Sony ... 28-75/3.5-5.6 ... but foldable design to make it really compact, when not in use .. "parking position".
- EF-M adapter included in package
- plus roadmap for new EF-M lenses to come ... see Sony! WA lenses first, because those will be smaller and lighter with reduced flange distance compared to EF lenses. No need to rush native tele lenses, since they will not be smaller. Size of front element is determined by focal length and largest f-stop.
Now THAT would have been a brilliant for a full-fledged Canon EOS-M system, which would gradually but quickly replace most DSLRs, except possibly a 1D type "fast action +long lenses" DSLR and maybe one Retro-DSLR for all those Retro-buyers who want a "chunky, beefy DSLR with proper mirror slap, OVF and lots of dials and buttons all over" [a.k.a. "Nikon Df"].
But no, ultra-conservative Canon geriatric management ward would never do such an innovative thing. So they goofed and are being punished by us, the customers, who will only buy their sorry EOS-M if it comes almost for free. Right on them! :-)