Would you want an APS-C camera with an RF mount?

BirdShooter7 wrote:

You are making the same mistake Olympus makes. Having the equivalent FOV of a 600mm lens does zero for me (and pretty much all the bird photographers I know). If that’s the only benefit I would just go with a FF camera and the 150-600 that I already have. What we want is the 600mm lens with the pixel density of the 90d, or maybe even more, without all the extra pixels of FF that we are cropping away anyway.

Not a mistake. Photography is about compromises and balance and meeting one's need. I have argued the case for having no RF-S, of having RF-S, of sunsetting the M line and keeping the M line. Why? Cause different people have different needs. 
And just as you mention FOV and DOF blah blah blah might matter to some and not to others. I consider myself a generalist when it comes to photography. I dabble in a lot of it. But end of the day my main muse and target is my little princess. I got into photography because of her. But I decided it was silly to spend all this money and time in something and not expand on it. So birding... would like to, sports, landscape, macro etc. 
For portraiture DOF is important, hence why I have FF. But I have a family and a kid which means my monetary priorities doesn't have me spending money like crazy on gear. I also don't have the time to spend on photography all the time. For that reason system consolidation is better for me than having multiple mounts. So having a crop body and long lenses for birding or wildlife that I might do 1-2 times in a year seems like a waste. So a high MP body that allows for cropping for when I do that... fine. But it would have to be faster than 5 fps. 
For you where it seems like birding is the main thing... then yes your point is clear and I don't disagree. Its just that people get fixated on their need and don't consider those of others. Hence why I am for OPTIONS. You know way way better than me what is good for you. 
Personally... I think an EF-M, RF (RF and RF-S) line is what canon should aim for. EF-M for those who will never go the upgrade path, and focus on cost, weight and size, and the RF and RF-S way for those who are more into photography where we can benefit on having both crop and FF with 1 consolidated mount. I would consider RF-S (for mounting FF small primes, and perhaps 1-2 RF-S longer lenses which would be smaller and cheaper probably than FF RF lenses)... but probably never EF-M.