Basically, it would be like GoFundMe, but users could also pay money to defund a campaign if they so desired.
For example, if there was a campaign that people thought was distasteful, they could pay $10 to take $5 from the campaign and allocate the previously funded $5 and $5 from the defund fee to the antithesis of the campaign (selected by a site administrator).
The remaining $5 of the defund fee would go to site operations, allowing the defunding payments to pay for costs rather than taking costs out of campaigns themselves.
This would allow sites to respond to pressure from the public about controversial campaigns with less threat of being deplatformed by their ISP, host, or payment processor.
Numbers are just examples, a lot of changes on the pricing and fee balancing would have to be determined, but the concept intrigued me.