In my column on Microblogging with RSS I'm proposing that, in the future, blogging software would be fused with RSS reading. (Think Tumblr with its "follow" functionality, but self-hosted.)
The Vouch proposal for webmention abuse would fit very nicely with this model, if we allow follow lists to do double-duty as "endorsements".
So each blog will publish a list of other blogs it publicly follows -- basically a list of its RSS subscriptions.
These follows serve the purpose of Vouch's endorsements. Another blog could then send you a webmention if you follow them, or if a blog you follow follows them.
This automates the process of creating a vouch for webmentions you send, although the bulk of the "work" is still done on the sender's end. The sender simply needs to look up the follows of all the target's follows and see if it finds itself in there anywhere.