'sparse' clone idea

I wonder if 'sparse clone' idea described below would avoid the most difficult part of 'shallow clone' idea, namely the [sometimes] need to un-cauterize history. See: (<7vac8lidwi.fsf@assigned-by-dhcp.cox.net>).

'sparse clone' begins like 'shallow clone': full history is copied down to specified point of history (cut-off or cauterization point for shallow clone), but instead of cauterizing the history from that point downwards, the history is simplified using grafts.

In the sparse part we need:
 * all commits pointed by tags (if we clone/copy tags) 
   and other refs (if we clone/copy those tags)
 * merge bases for all commits in full, and in the sparse part,
   _including_ merge bases themselves
 * all roots

Commits in sparse part would be connected like in original history, only skipping "uniteresting" commits.

Thoughts? Comments?