I don't know the answer to the mix old/new compilers question but it looks like it's only the directory structure of the compiled artefacts that's important rather than the directory structure of the source code. It looks like you could keep all your source in one directory (unlike Java IIRC) and then compile it with `-I` and `-P` options.
This sounds invasive. Will it be possible to mix old/new compilers? (Because we support a large variety of platforms, some quite old, we cannot just upgrade everyone's OCaml compiler to the latest version all at once).
Plus I've never found systems like Java where module names follow directory structures to be very pleasant.
You might want to take a closer look who proposed this before being so dismissive.
Can we stop posting proposals or RFC's people have submitted as "X coming to Y" - namespaces would be handy in ocaml, but until I see a patch with serious consideration from the developers on a mailing list/github/issue tracker/whatever it's nothing more than a POC.