It would be nice if Canon could engineer a 30mm f/2 pancake lens. Make it even more pocketable.
Yes, I'm putting a lot of hope in them making a couple great apc specific lenses for this system (I don't need a whole system of lenses). One, like you suggest, would be a nice normal-ish pancake, the other would be a smaller "all-in-one" (something shorter in size than the 18-150). When I shot FF nikon, I loved their 24-120 as a grab-n-go solution. So maybe an apc optimized 15-75mm could be a sweet spot, not sure what this mount allows them to get away with.
I like the idea of a two-lens combo like that for the R50. Canon M series has a 22 pancake I believe, I would take that. I have the RF24mm 1.8 macro, which is probably my favorite RF lens, but kind of big/heavy for the R50. Give up a little on the aperture side and drop the stabilization and hopefully, a pancake in that 20-30 range will show up. Overall I'm very pleased with the snappy-ness of the R50, the primary complaint will be the grip, but anyone that actually wants the R50 would know that's what they are getting going in. If you want something like this as your primary camera you would probably get the R10 instead.