It sounds like this donor want you to operate like a DAF without the associated regulatory oversight. I am not sure I would go there and I suspect your CFO might not like the idea.
If anything, I do not think a deductible gift would exist until funds were moved from the holding account to an internal fund that is defined by the IRS as charitable and deductible. This approach follows the CASE standards on how and when to count gifts when a donor contributes to an institutionally-managed DAF.
John
John Taylor Principal, John H. Taylor Consulting, LLC 919.816.5903 Big ideas; small keyboard