hi rhermsen,
Unless you have a reasonable numbers of users I think the effort involved will be too great to be worthwhile.
The existing TCL software really expects the repositories to be mirrors.
Once an extension is downloaded there is no mechanism to determine which repository it originally came from. This is not a problem is the repositories are up-to-date mirrors. So for your unique extensions you need to manually change TCL to point to the appropriate repository. That is ok if its for just for yourself but its complicated for users.
If you go ahead, the repository needs to follow a specific directory structure and there are files and scripts, in addition to the extensions, that are required and are not generally available.
regards
Greg