One key problem is the need for "fiducial oversight". That is, a grant organization needs to know there is a professional accountant who manages the funds and receipts.
Rich Hickey can do the open source world a favor by sponsoring a couple full-time funds management "fiducial oversight" professionals (aka an accounting firm). These 2 or 3 accountants could handle grant fund management for a large range of open source projects.
Block grants could be given and distributed to multiple open source projects based on their grant proposals.
Universities have this. The only grant I got was at a university. The provost took about 55% "for support" but I did get my research funded.
Perhaps somebody who knows somebody who knows Rich could pass this along.