I would prefer a 90mm lens, but that is pure personal preference. One reason why I like the Olympus 45mm so much. Great lens at an affordable price.
See above, my disliking of 50mm as portrait prime is my personal opinion. YMMV
Instead of building on the extensive M userbase and fill in the gaps in the lens line up we get the same shoddy stuff we already have with a new mount. I dont see the point.
If you're talking Olympus, then you're into 4:3 territory.
Crop the ends of a Canon 1.6X APS-C 3:2 sensor to 4:3 you have a diagonal that puts you at ≈1.75X crop factor.
So now your 50mm Canon lens yields an AoV
very similar to your 45mm Oly lens. (43.75mm in "µ/3 equivalent" vs. 45mm - lens' actual focal lengths are often rounded more than that to the number they're marketed under.)
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The vast majority of the M user base worldwide never buy another lens after they buy the camera and whatever lens(es) they buy with the camera. They're not the same market as camera gearheads that are constantly looking for a new lens or body to yearn for. They're not the people that are looking for any "upgrade path". They're not vloggers than mindlessly follow the leader any time someone on YouTube tells them whatever they're using is now "trash" and they
must upgrade to the latest new toy.
They're the folks who are looking for a dedicated camera that is relatively compact, relatively light, and relatively inexpensive that they can use for special occasions, vacations, and other use cases when a smartphone isn't quite enough. They're then happy to use that same camera and lens(es) for the next several years.
They're also mostly in Asia and emerging markets in other parts of the world, not in the U.S., Canada, and Western Europe (+AUS and NZ).