I do my scanning currently with a Lumix G 30mm f2.8 ASPH fitted to a GX8. The 4:3 sensor captures sprockets/film edge details etc. just fine and even if you crop down to 3:2 you're still getting all the detail almost any 35mm film frame can muster at 20mpx. Even for 6x7cm etc. a single capture is fine for digital sharing or storage. I'd only bother with stitching multiple captures together if I needed a really hi-res file for large scale digital printing.
Speaking of stitching multiple shots, distortion in macro lenses can introduce artifacts into the final combined image ... seems to be where the trend of using an enlarger lens and bellows has been developed from.
My understanding is the G9, G9II and Olympus OM-E Mk2-3, EM1x and OM-1/OM-1m2 can all do pixel shift hi res shooting. Must admit I loved that feature when I borrowed an EM1x way back... they're coming down in price massively these days.... hmmm....
I am curious to get a 100mm macro lens for my Canon 6D and see if the larger sensor size (same overall resolution) improves DSLR scan quality. The 6D works better tethered too (in my experience).
Truth be told though, I do hope to get a Sony A7Rii one day, primarily for DSLR/mILC scanning, when the prices drop a bit further.