It's been years since I looked at Mixmaster stuff. There was some really interesting stuff being done with anonymous remailers 20 years aso, and I haven't really kept up. Might have to look into it again. Seems the time is ripe. Gotta figure that half the nodes are Fedgovs, as the ferals don't miss a trick, and they have an infinite amount of money.
The problem with relays is that they are susceptible to DDoS if they’re not secured properly. Even routing your network traffic through multiple VPNs and TOR can be tracked if you have the know-how.