For the unverified users, why not automatically whitelist PoW pubkeys above a certain threshold?
People could
- mine themselves using rana or nostril (proof of work, they would not want to risk throwing that to waste by getting their key banned for going against your ToS), or
- pay a miner to mine one for them using PoW Pub ( https://lab.oak-node.net/powpub ). Running a miner could be an extra source of revenue for easyNostr.
Either way it could be an easy way to keep spammers at bay.