Hello, another user here with similar thoughts.
I solve parts of the abstraction layer you’re asking about through CI (github actions); for instance, iterate through secrets and pass them to flyctl - or knowing which file to use for what environment, or releasing ip’s as part of an initial setup.
Making this more robust is probably best achieved by using their graphql endpoint to interface with; but I haven’t gotten to that point yet. It would be interesting to collaborate on a github actions project that would hande a lot of the plumbing at some point.