I think it would depend. For many charities, the ultimate cost of this sort of "strict liability" policy is borne by the intended beneficiaries. I would be hesitant to extend in certain cases beyond what I think morality requires.
For a grad student receiving a micro grant, asking to return funds already earned is too much, and expecting significant vetting is unrealistic and inefficient.
The potential value, I think, would be for midsize+ organizations with a diverse donor base. They could put e.g. 5% of each year's donation into a buffer, releasing 1% each year to programs as time passed without any red flags.
Very few nonprofits could absorb a reversal of a megadonor's gifts.
Thanks for writing this! I think this is a good proposal worth seriously considering and engaging with (although I'm undecided on whether I'd endorse it all-things-considered).
One other consideration is that you may want to effectively negate the benefits obtained through fraud to prove that "crime doesn't pay", and this means decreasing budgets for the causes by the amounts granted/donated to these causes, by cause. Since FTX and associates were disproportionately funding longtermist interventions and presumably value them more than other causes, if we don't pay out disproportionately from our longtermist budget, FTX and associates get away with shifting the share and amount of funding towards longtermism, which is still a win to them. (Of course, this doesn't necessarily mean the share of longtermist funding from outside FTX should decrease overall, since there are also reasons to increase it now.)
Another consideration is that we should pay more than the benefits, to account for fraud that isn't caught.
Both good points.