There used to be teTeX (https://www.tug.org/tetex/ https://www.tug.org/tetex/) which allowed installing packages separately, but that's no longer maintained. I

There used to be teTeX (https://www.tug.org/tetex/ https://www.tug.org/tetex/) which allowed installing packages separately, but that's no longer maintained. I think KerTeX (http://www.kergis.com/en/kertex.html http://www.kergis.com/en/kertex.html) now allows a similar style of pick-and-choose package installation, but it doesn't support a lot of packages (yet?).