Hello Luis
Yes, I know this process, but on vagrant, since this is a boxed operative system, have a shared folder like shared folder on virtual box (this is a provider on vagrant), then, is needed to setup up a folder inside the installer o some place, since the [path-to]/health$ is shared, it could be something like the follow folder list, then the provision script could link them to the local path server ( adding local to .hgignore ), them each time is there custom modules, it could be placed on local and using the $ hg npull -u we could keep our local repo and custom modules updated and deployed into vagrant box ( just on how I think is there is no yet a was to manage it )
[path-to]/health$ ls -l
total 12
drwxr-xr-x 2 csotelo csotelo 4096 abr 11 12:05 local
drwxr-xr-x 4 csotelo csotelo 4096 abr 6 10:21 misc
drwxr-xr-x 44 csotelo csotelo 4096 abr 6 10:21 tryton
Best regards