I'm going with the latter obviously of the two scenarios presented above.

Now I'm looking to get that nice 11-22 wide angle IS lens for an upcoming trip to the Grand Canyon....

I'm in the same camp. Picked up the M to lighten the load when hiking, no regrets. Even with a full complement of lenses (22, 11-22, 18-55 and EF-S 55-250 IS STM), it's only about a third the weight and space of my 6D kit (40, 17-40, 24-105, 70-200 F4 IS, 1.4x III) and gives me greater reach (17-400 equivalent vs 17-280).

I sometimes want a longer lens on the trail and the 55-250 has been a pleasant surprise on the M. It's around twice the weight and size of the other zooms (including the adapter), quick focusing, silent, and is easily handheld - even at 250mm. An EF-M variant might save half the difference in weight and space from the other EF-M zooms if it ever arrives. And it will probably cost more so this will do until then.