Creators are always in need of promotion and critics/promoters are seemingly always in need of reliable revenue streams.
itchio could bridge that gap by allowing people to create storefronts (like collection pages) which adds a cut or tip on to the product's price for them. Conceptually identical to running an actual store. This should give promoters a reliable revenue stream (reliable in the sense of them actually knowing the causation of how and why they are getting money -- their fans buying games through their storefront -- rather than the nebulous causation of syndicated advertising) and incentivize them to a more symbiotic relationship with more creators than what other funding incentives.
The creator and promoter never need to interact for this to take place so it dodges any idea of conflict of interest.
As far as vectors for abuse of a system like this... creators having opt-in control should be more than enough. Maybe a limit to the amount of profit that can be made on top of an original price if you want to be extra diligent.