Just throwing this out there again, I have been looking and looking for a solution. I tried to build my own useint the ACF block builder today gave up after 8 hours of getting nowhere…
I am currently using Kadence Blocks for this, as a temp solution. FYI they have a dynamic gallery block.
I always come back to this, thinking that acf gallery to sliders can be quickly done in cwicly 
(but then remembering that it only works with repeaters)
Seems like a missing piece of the puzzle.
The issue with this is that i manage my cpts using wpsheet, and iwith a repeater field each image is treated as an individual column… so with a gallery with say 100 images, it creates a column for each image. I like the ability to copy and past all of the image in one column from one cpt to another or even from one site to another with wpsheet. But that becomes nearly impossible with the repeater field. Even if i can upload them all at once. Make sense? I am looking at some other options though for storing the images like dynamic folder creation etc… as it appears the slider feature for galleries is not going to be happening any time soon and the Kadence blocks are causing other issues, and I tried for almost two days to creat my own ueing the acf blocks ( I dont write code but was trying to have AI help me with it). so i have given up and for now am setting up the repeater with a 10 image limit for the header galleries.
Can we think differently and add a rotating display style with thumbnails to the existing gallery block?