The weak point in the randomization is the validators. To perfect randomization, Pseudonym Pairs will likely use a commit-reveal scheme. Each person commits random numbers during registration phase. When it is time to reveal, registration is already closed. The random numbers decide positions in pairs that will be swapped. Impossible to attack by validators, they have no say in it. That said, validation in Nakamoto consensus is good and well designed. This is just to have perfect randomization. The test net I have deployed is still secure, perfection of the randomization is only needed as population approaches 7 billion, and what I just described can be implemented in 5 minutes. I am currently registered with person registration number 2 on test net, valid for 4 weeks :)
The receipt for the transaction that claimed my proof-of-unique-human is here, https://ropsten.etherscan.io/tx/0xf6d6c9aae85da22933769f0d020e3ce15b6359a2faacedd8521cd742fcf47703.