Soon after its release, I bought a Canon EOS R, primarily for video (which is a minor part of my business) and to compliment my 5DM III and 5DM IV, for which I have many EF L lenses. I recently sold my 5D MIII and EOS R and bought an EOS R5. Fortunately, I have the Canon Control Ring adapter, so I can use all of my EF mount lenses with the R5. I shoot mostly Real Estate/Architectural photography and do a lot of headshots (using the EOS R with EF70-200 f/2.8L II). I will continue using the 5D MIV for the real estate work mainly because a 45MP photo is way larger than what I need for that work, which needs only about a 4MB photo. My plan is to start selling my EF lenses, starting with my EF 70-200 f/2.8 II (which I use for headshots) and eventually replacing them all with RF mount lenses. I'll probably only keep my EF 16-35 f/4L because that is what I use for real estate photography. I wish that Canon would make it possible for the EOS R5 to adjust the size of the photo as is possible with the 5D camera (from 10 - 30 MP). I prefer Canon lenses over third party lenses, but the RF lenses are REALLY expensive. I remain hopeful that Canon will allow third party manufacturers like Sigma and Tamron to release RF mount lenses. I would most likely still purchase the Canon. My thought is that Canon is hesitant to do it because competition will force them to lower the prices on the RF lenses, which at the moment seems to be their golden egg. I think the patent issues is just an excuse. The real reason is the money, at least in my opinion.
Canon, if you are reading this, I have two requests:
PLEASE Enable the EOS R series bodies to produce various output sizes like the 5D (until that happens, I have to keep my excellent 5D MIV), and
Let third party manufactures make RF mount lenses. Don't be afraid of the competition. You might have to sacrifice a little margin, but I am quite sure that you make up for that with sales volume from people like me, a CPS Platinum member, who prefer Canon lenses over Sigma, Tamron, etc.
You might want to look in the Advanced User Guide on P757, to see how to set an image size as part of a file-naming string that is assigned to a custom setting. I wonder if this might resolve your issue until Canon does an update to the firmware.