I like a bit of vignetting too. With straight up black I was referring to the 24-240mm which has an image circle that doesn't cover the entire sensor at the wide end. If you look at the image height of the patents, you'll see they also don't have a FF image circle at the wide end. Canon simply applies a profile which crops the image to effectively reduce the sensor size to something that is covered by the smaller wide angle image circle. I just don't feel good about that approach. But that's just my opinion, nothing that should matter to you. I'm not saying it is a bad move by Canon to investigate these new options!
I too was skeptical, but as I was preparing for a trip where I needed equipment to be compact and ready to shoot in most situations, and for that the RP and RF 24-105L (that I love) lack the telephoto reach, so I would have to add the 70-200 4LIS or 70-300 DO to my bag and do lens changes (or schlep the 5DIII). When I saw the promotion RP + 24-240 for $1,500, I saw an opportunity to give this new approach to high range zooms a try. One RP will have that lens, the other one the EF 16-35 L 4.0 IS with adapter for the select pictures requiring very wide angle and/or high quality in the 24-35 range.
Some thoughts about the 24-240 and the use of processing to correct and upsample images: 10 years ago I was shooting weddings, portrait and travel around the world with my 5D Mk1 (12 megapixels) and loving my pictures. If the 24-35 range of the 24-240 zoom is effectively re-sampling a reduced image circle of 18 or 20 mp this is still a very acceptable resolution for my picture galleries and books. Making use of RAW in the 24-35 range is not going to be easy due to all the corrections needed, but this may be irrelevant. I find with mirrorless that I have so few poor exposure situations JPEG out of the camera is not as crazy as it would be with my prior DLSRs, where I often had to correct 1-2 EV in challenging lighting situations, making RAW indispensable.