With wider adoption of ipv6 and all the good things that come with it (don't mistake me, they are great!) also comes the risk that each computer will get a uniquely identifiable IP address that will be used for fingerprinting. I've never really used Tor in the past, but this got me thinking about it.
An option could be to provide a webRTC-based node, but I am not sure how feasible that would be, after reading some comments here. Maybe for entry nodes and guard nodes instead of exit nodes? The transient nature of browser sessions could greatly enhance privacy. Of course, you would need some algorithms to deal with this very nature... But I can imagine some.
This surely lowers the barrier to entry for greatly enhanced privacy. Quite a lot of people seem to be aware of the private browsing mode, and I can imagine this being turned into a simple toggle on the private browsing home page, along with a short explanation (and a link to additional privacy tips).
A low hanging fruit that could enhance the privacy a bit would be to use the trusted recursive resolver (DNS over https) in private browsing by default, since it already is part of Firefox. It just needs a default trusted resolver.