Determining individuals is basically impossible to do and is easily gameable by individuals such that some people get more power than others without those others necessarily knowing.
Also, Bitcoin doesn't use 51% mining power for anything except 51% attacks.
filesharing, take a picture of your eye/fingerprint, gg wp. (it is already built into the ardor/bitswift network) The filesharing can check for dupes on the blockchain, so you can only have 1 account, in theory.
here is a eye captcha https://www.youtube.com/watch?v=l4x0vOAu0lQ
you can do the same with fingerprint
here is the file sharing https://youtu.be/Y7TLFyK_3Pk?t=965 I explain it briefly in this check out www.bitswift.network wallet (login top right). p2p exchange, file sharing, decentralized voting, asset creation etc.