Its taken a while, but its nice to see a helpful feature added to win 7 SP1.

http://blogs.technet.com/b/askpfeplat/archive/2013/10/07/breaking-news-reduce-the-size-of-the-winsxs-directory-and-free-up-disk-space-with-a-new-update-for-windows-7-sp1-clients.aspx