@johnh, I’m well aware of modules. In fact, I kind of recommended them two days ago (Handling multiple versions of Julia - #2 by carstenbauer) 
I want to set up a centralized installation of julia in a multi-user institution network. So far (<v0.7) I could basically only provide the binaries and every user has it’s own .julia. This leads to packages and so on being installed many many times.
WIth Pkg3 in Julia 1.0 it should be possible to also have some popular packages in a centralized julia-depot folder somewhere (see doc quote above).