I wrote a python scrript which was looking for dell mirrored drives to put the OS on for a disk commissioning script some time ago - it’s not perfect, but it might be a good starting place instead of trying to tweak OS images and the like.
While it would be nice to have the drives in the order you want, it works just as well as sdz instead of sda - and you would have less difficulty with tweaking curtin images and all that.
I was facing similar issues when all my 12t virtual drives would show up before the 512g mirrored ssd pair I wanted to use for boot devices.
Take a look at this thread: Custom storage layout configuration examples
Thanks
~~ Charles