Hi… I would like this, too, but it has been formally requested and formally denied:†
(That was only one month ago.)
I’ve added the wishlist tag to your post, which is the closest there is to a feature-suggestion tracker for this side of things.
This part can be undone retroactively, as has been mentioned in basically all recent threads on billing limits.
Not everyone is happy with this as a substitute, but the arguments pro and con have really all already played out now.
†Idiomatically, “at the moment” means that the present decision holds for much longer than 4 weeks—but I don’t speak for Fly.io in any way.