Not harmful for now - "fork from checkpoint" would be perfectly fine for me at the moment. The main issue (as flagged in the post) is that setting up additional tooling can take a while!

In the longer term, docker is nice from a reproducibility + CI perspective, and a docker build is already something can easily work with and track in my system.

One thing I've heard but not verified with other sandboxed execution providers is that startup times for custom images can be quite slow, so it could be a potential differentiator given Fly's existing infra.