It isn't difficult to be fair, but it is still a lot of work.

Enter all qualifying requests, in the order they were received, into a spreadsheet with varieties in top row, requesters in left column.
Columns provide cutting request totals for each variety.

If the requested total exceeds qty available, those requesting multiples of the same variety will receive less. He basically says this in the instructions.

If the requested total exceeds qty available even with each requester receiving only one order, then he is looking at 1/2 orders.

If the requested total using 1/2 orders still exceeds qty available, then it is likely 1/2 orders will be filled until exhausted and some of the requesters may not receive any.

At this point, he'd likely contact requesters with the availability. The requesters then pay based on availability.

If the availability includes 1/2 orders and some requesters do not buy them, he'd likely contact requesters who were originally told they would not receive any of a particular cutting.

Any requests after the 3 PM deadline earlier this week will likely be filled in the order received for the quantities requested, no matter how large to help ensure as many cuttings as possible will be propagated.

Wider spread propagation is a goal of the Foundation, and 1/2 orders are more effective at achieving that than full orders or a few large orders. It is possible some requesters may make the arguement that they will spread propagation much further if they receive a larger order but that can't be quantified reliably.

I'll be happy with one cutting of each (with the price reduced appropriately);).

  
In hindsite, I would have made a longer request list.