Onchain Builders: Expand user metrics beyond Farcaster IDs

### What are you providing feedback on?

Metrics - feedback about the metrics used in the Eval Algo

### Please describe your feedback

This issue captures feedback raised by multiple community members [here](https://gov.optimism.io/t/retro-funding-s7-onchain-builders-eval-algos/9708).

Feel free to comment / add more ideas!

## Summary

Community members have highlighted concerns about relying on Farcaster as the primary (or exclusive) onboarding mechanism within the OP Stack ecosystem. While recognizing Farcaster’s advantages (e.g., being built on the OP Stack), people urge considering additional options to prevent gatekeeping and provide alternative user metric derivation methods.

## Background

- Farcaster is currently being positioned as a key part of the metrics models, but in the long run we want more than one source of user numbers.
- For any user model, the risk of Sybil attacks and bot accounts is real, but can be addressed through multiple verification strategies.

## Proposed Solutions

*Note these come from the discussion, they have not been prioritized for impact or feasibility*

1. KYC-Verified Users
- Leverage Gnosis Pay (or similar) cardholder data, which is KYC-compliant.
- Although the total number of these users may be limited, analyzing connected addresses could identify user patterns and potential trust scores.
- See also: [Dune Query #4120201](https://dune.com/queries/4120201)

2. CEX-Linked Addresses
- Use addresses associated with reputable centralized exchanges (e.g., Coinbase, Kraken, Binance).
- Filter these addresses by additional metrics (Optimism activity, account age, balance, attestations, or Superchain engagement).
- Potentially incorporate the existing Superseed participants for more robust data points.

3. Non-KYC Addresses
- Filter by meaningful onchain activity (transaction history, account age, or asset holdings).
- Employ heuristics to discern legitimate users from bots or Sybil attackers without requiring full KYC.

### Please provide references or examples

_No response_