I rather think that devs' time would be best spent ensuring that our tools against Tor users and open proxies are effective and reliable. Huge amounts of volunteers' time are spent combating abuse of them, with inadequate tools. See for instance: https://bugzilla.wikimedia.org/show_bug.cgi?id=30716 https://bugzilla.wikimedia.org/show_bug.cgi?id=42438 https://bugzilla.wikimedia.org/show_bug.cgi?id=8475
As for legitimate users, probably the most useful thing to do would be ensuring that the TorBlock extension shows an understandable error message and sends people to a translatable page with instructions valid for all language editions of our projects with current poliecies (most projects will have none).
Nemo