This is the main thing I miss about subversion. You could check out any arbitrary subdirectory of a repository. On two projects the leads and full stack people had the whole thing checked out, everybody else just had the one submodule they were responsible for. Worked fairly well.
Mercurial has narrowspecs these days too! Facebook's monorepo lets you check out parts of the overall tree too. It's not like every Android engineer's laptop has all of fbios in it.
Would you mind explaining about this lack of seamlessness?
I can imagine that part of it could be the need of a git clone --recursive, and everybody omits the --recursive if they don't know there are submodules inside the repository. There is another command to pull the submodules later but I admit it's far from ideal.
