How about two different Versions of the Installer? One Offline-Installer, which contains everything (so Music too), and one smaller, which downloads the Music. Would find that more user-friendly. Deactivatable as it is for now.
Possible to reduce the Size of the Online-Installer more and more by making it downloading all the Mods - then you always have the newest Version of them. Other Things could be downloaded too. Recommend is a Download-Database, where the Authors can update their Products, but since not everything changes often, you could already build that without Problems. You just need Time. And Will.
Whole Idea goes to an Auto-Updater again, heh
By the Way: The Installer doesn't delete the Startmenu-Entries. No Version/Release did that at me. Other Files too: stderr.txt, whole Game-Folder. 