I had a very specific question in mind, but I came across a few things that I’m going to just leave here in case someone else finds them useful.
Turns out there are decent people doing all sorts of wild things when it comes to nested packages. Looks like ModelParameters.jl does the inverse of what I mentioned, equivalent to putting PackageFull is in a subfolder of PackageCore: GitHub - rafaqz/ModelParameters.jl: Easy, standardised parameter get/set for heterogeneous or nested immutable models.
Something I hadn’t thought of is how the folder structure is going to interact with repositories. One approach suggests having a Repo folder, where the packages are in their own subfolder, but then the repo has a Project.toml and Manifest.toml: Feature request: scan subdirs for updated versions/projects · Issue #1874 · JuliaLang/Pkg.jl · GitHub
And more discussion here:
I don’t know where I’ll land. Some paths are more well trodden than others and the approach of using include() does not seem to be one of them.