It sounds like a submodule... But certainly if the problem could be solved with a submodule, people would have found out long ago. Git's submodules also support shallow-cloning already [1]. I can only guess what the issues are with large files since I didn't face it myself - I deal with pure source code most of the times. I'm interested to know why it would be a bad idea to do that, just in case. The caveats pointed out in the second SO answer don't seem to be a big deal.

[1] https://stackoverflow.com/questions/2144406/how-to-make-shal...

It sounds different to me - a regular git submodule would keep all history, unlike a file storage with occasional snapshotting.