I've been meaning to do this for a while and almost have it finished. An SDK is a much better fit for the OST than a library. IC will need to auto-update existing OSTs to be an SDK and remove the library representation. I'm also trying to generate the OST into an archive rather than as an exploded directory structure. This helps with file system pollution and implicitly creates a read-only SDK. It also seems to address the issue I've had that's required module content roots to be children/descendants of the project root.
Issue #158 resolved