To be sure, flyctl cmd that didn’t work for you looked like this:
flyctl scale count worker=1 web=8 -a my-multi-proc-app
If so, that is surprising, as it is exactly the usecase multi-process Fly apps were built for.
I don’t think that is quite true. Can you link to the documentation? I ask because this forum post indicates multi-process Fly app should work with multi-region deploys just fine (in fact, we did use multi-process once ourselves and from what I recall, multi-region worked as expected with autoscaling disabled).