My thought process was just that centralised platforms like twitter have far more control over the on-ramps of new users and still failed to solve the issue. And from what I’ve seen I think it is fair to say that the current spam is still quite unsophisticated
Paid models have a new large unexplored solution space where is see many promising options like paying $10 at sign up and getting it back after a week or whatever.
Anyways, I would love for you to succeed and happy to support if I can