but what if you used tor normally, not through your own bridge, but through "regular" randomly chosen 3-hop circuits and at the same time run a tor relay (entry/middle)
This wouldn't require weakening the tor circuit model anymore. Yes, this is correct. The more Tor traffic goes through the machine that identifies you, the more confused an adversary is. It also makes naïve correlation attacks impossible,⁽¹⁾ and increases cost of more advanced ones.
That is great news mpan, thank you. That would incentivize users to also become relays - why isn't it recommended more often? This is the first time I ever hear about it and it sounds like a powerful idea. Normally I only see tor relay operators claim that they run tor relays purely altruistically: https://www.reddit.com/r/TOR/comments/6znjkg/why_would_anyone_setup_a_tor_re... Are you aware of any articles from torproject or research papers confirming that hosting tor relay at your own IP does in fact help your own traffic blend in? I've looked through all tor proposals (https://spec.torproject.org/proposals) and many research papers (https://www.freehaven.net) and couldn't find any mentions of this?