Actually it works quite well - and you can do it not only in a single plane.
I made several panorama in the 90s with the 24TS in this way. I think it made more sense then when even ISO100 film grain was so big, but even then the sharpness fall-off was pretty severe.
Given the 45MP R5, though, and how sharp today's RF glass is in the center, I suspect cases where say a center half of a 45MP 35mm image (22MP) is notably inferior to two 45MP 50TS images stitched together (call it 75MP) would be very very small. I like resolution IN THEORY, and of course 3.4x the pixels sounds great, and has a certain intellectual satisfaction...
... but what use case would actually USE those pixels? I mean, I usually edit personal photos to 1500x1000. That's 1.5MP. No photo on the internet seems to be so big. Billboards are too far away to really see more pixels. Magazine printing probably doesn't have the resolution. Maybe doing a big panorama on a wall in an office that people CAN get close to? And how many times does someone on this forum make such output?
(Really the great thing about 45MP, to me, is that you can crop the heck out of photos and still have something totally useful. But by definition, in this panorama proposal, you are not cropping out details.)
And yet, while you have 3-4x the pixels, you also have substantially less sharp the lens performance. Lenses with a large image circle have a lot of fall-off of sharpness towards the edges, and in an apples-to-apples comparison you're comparing the 43mm-wide image produced by the normal lens with a 63mm-wide image produced by the shift lens. A defect in the lens manufacturing will simply be magnified 1.45x on the shift lens. You don't magically get a lot more lines of resolution at a given contrast just because the image circle is bigger.
And swinging a shift lens from max left to max right shift is hardly a chore anyway!
In short, you and the OP are arguing:
-- this ultra-rare media usage is nonetheless somehow common enough,
-- and having the extra MP despite no increase in IQ is somehow so valuable,
-- that we will make the first motorized shift lens in human history to satisfy this ultra, ultra, ultra, ultra niche.
In contrast my argument is:
-- there are enough people who use AF for single points in a scene,
-- that I project there would be enough people who'd also like AF for 2 or 3 points in a scene,
-- to make this valuable.
I mean, how many photos have two-three objects at different depths that you'd like focused? I'd guess something like half of them, no?