Hi @nrdxp + @edolstra -- I have a couple ideas for how to make things marginally better here but, tl;dr: I'd like feedback or direction from either or both of you on my idea before I invest more time, especially for exploring the proposed solutions that require C++ development. (Also, please let me know if you'd like me to move this from an issue comment to an RFC or even a, e.g., Google Doc design doc, for easier interaction.)
In my words at a minimum:
flake authors need to be able to request submodule-fetching for the repository hosting
flake.nix
(Please see my appendix for supporting use cases and UX/DX considerations if you aren't already convinced about this need. Also, @nrdxp, please let me know if you actually have a different motivating problem in mind?)