Previously, Gamocosm always downloaded the latest version of vanilla, and to install different versions of Minecraft, you had SSH or FTP and change it yourself. A few days ago, I added support for having Gamocosm install different flavours on a new server (the setup workers have also been refactored and optimized), and I’m happy to say everything seems to be working smoothly!

You can check out the repository of install scripts used (like how the OSX package manager Homebrew has a repository of formulas). This wiki page includes instructions on adding support for new flavours, and manually installing something else yourself.