Chris,
Cow Paths: Yes we have this concept in both New Urbanism and planning municipal bike/hike trails. It’s a good analogy for what I’m doing: “What’s available off the shelf and free as a stopgap until somebody designs something better?”
Blog Discovery: I’m sure directories are not the best solution for blog discovery, but like blogrolls they have a place at the table because they are low tech and cheap. Here’s a rough hierarchy:

Do In A Pinch: Blog acting as a directory.
Minimum: A proper directory script (ie. phplinkdirectory or similar) This allows for blog owner to submit their blog, write a description etc.
Better: A directory script that not only lists blog URL but also lists blogs RSS feed.
Better x 2: Directory described above which also generates it’s own RSS feed for each category and subcategories.
Better x 3: Some sort of fusion of the x2 directory above, and Indieweb stuff to some degree. Maybe a fusion of a standard directory with Kicks Condor’s Indieweb.xyz. This is just brainstorming.
Better x 4: Probably an RSS search engine like the old defunct Daypop. Because this leads the searcher to individual posts about a topic in close to real time. Such an engine could use Post Kinds as filters for the searcher to refine their search. There used to be a lot of RSS blog search engines I could find only RSSMicro today.
Best: Some sort of hybrid directory/RSS/crawler engine listing only blogs. The search crawler digs deep into a blog for those posts from 2015 or before that are buried and won’t appear in feeds. The RSS search engine for the newest posts.

Something like that.
I don’t think we have tapped RSS fully.
OPML: I use Inoreader and I subscribed to your Indieweb list from your Following Page. Brilliant list and thanks. I think there is a future for this for deep discovery.
rel=directory: My instincts tell me this is important and they are on the right track. The directory also is a low tech way to sort by topic. Because it’s not enough to just have all the Indieweb plugins, but people need to know what the blog’s topics are.
Vouch: Yes. Needed in some form. I used to move at the periphery of the spam crowd although I was never part of it and I can tell you, right now Indieweb stuff, (webmentions etc.) are in a honeymoon. The spammers will figure out how to exploit these in ways you never dreamed of.
Thanks to you and to Kicks Condor for taking the time to reply so extensively. The first step needed for Blog Snoop is to have an extensive index of blogs. Only then will it be of any use. And this was a useful discussion because it gave me some ideas that might work. Again thanks.