That's a fair point, but given they would be the ones writing it, I think they could work around it. An organization could write up something like this and still provide themselves with avenues for selling collections upon their impending closure; they could write it up without necessarily impeding their fiduciary responsibilities. It would ultimately be up to them in how they write this up, because I'm sure however they write a will like this would vary to varying degrees from the example I provided above.
RE: Where There's a Will, There's a Way: Creating a Document Directing Deaccessioning Upon a NonProfit's Demise