I have never heard of an arrangement like this before. I think
some issues to address are (1) would your museum purcahse
the art work if it were for sale (because if you must meet this
clause, that is exactly what you will be doing) and (2) I would
try instead to strike a deal where each year the museum obtains a
percentage of the ownership title of the work and avoid all
together the issue of market vale. The ideal (since they won't
outright give it to you) is to own free and clear as much of the
work as possible, gaining complete title to the work within a
specific time period, let's say, over the next five years. This
type of arrangement is becoming more and more common.
The arrangement as stated, does not appear to leave your museum
much recourse, and also leaves you prey to someone else's poor
money management.
Good luck.
John Handley
[log in to unmask]