This is a great research area that it would be good to see some attention for.
Alrighty... I will try to find time to resume work on this soon. I'm hoping Meejah or Jean-Paul will help me with this. I've always thought this would be a fun project to do for Tor and now that you've expressed interest, my interest is renewed.
In particular, if there are specific relays that are doing especially poorly for connectivity, we should work with them to try to get them to fix it, and if it's unfixable, downgrade their weights and/or boot them from the network.
See also https://trac.torproject.org/projects/tor/ticket/12131 ("Measure connectivity patterns between relays") and https://trac.torproject.org/projects/tor/ticket/19068 ("Write and run a clique reachability test")
--Roger
Cool. I had no idea there were trac tickets open for this already.