We created a prize for presenting the best ideas in regards to this and some winning ideas came from Umar Khan, Colton Orr, Kyle Weiss, and Gordon Berger. 
It can be seen here: https://www.viaprize.org/campaign/67/write-out-a-non-kyc-way-to-vote-on-bounty-winners

In the end, the idea we implemented by writing open source smart contracts (https://github.com/viaprize/Viaprize_contracts) involved using directly proportional allocation of funds combined with verified users with the gitcoin passport. 

The way it works is that funding for a prize is supplied through crowdfunding. The funders vote on who wins the prize money. It is directly proportional meaning that if a contestant earns 20% of the votes then they receive 20% of the reward. 

There is directly equivalent voting power meaning if someone added 20% of the funds they have 20% of the voting power. 

We have zero KYC which could be an issue for the Sybil attack, except this directly proportional allocation solves for it because if someone votes for themselves, they would only get their own money back. As well as this, the votes are hidden until the voting period is over meaning that someone voting for themselves does not alter other people's decisions.

That being said, this is for retroactive funding. Considering that staking funds to a project convinces peopel to build the project, we still want to make sure that these potentially anonymous funders vote on good projects. 

In order to solve for this, we make it so that unverified users only have 50% voting power. 

They may have full 100% voting power if they become a verified user with a gitcoin passport. 

Any unused voting power may be allocated by the admins. 

This helps protect project builders but also helps funders because if no good project is built then funders can be refunded.
This de-risks funding and offers an alternative to grants. 

We are continuing to research about how to improve these solutions, how to select admins, and are chatting with the Gitcoin team about how we could work together and expand the model to consider other options including retroactive public goods funding. 