It seems we get a lot of similar requests. I think they are realky wanting a "AS Is value in Fee Simple" but just dont realize what they are asking. I would ask the send another engagement letter requesting exactly what they want, then provide them exactly that. Then there will be no confusion. I tend to agree that you have done what was asked and required. As far as to what interest the bank would have in foreclosure, that would depend on the terms of the mortgage and the lease terms. But personally, I would ask a revised letter of engagement, then explain the difference in the report so the reader would understand which interest was value and why it was done that way i.e. "The property is currently subject to a long term lease that appears to relfect current market rents and terms. However at the request of the client, the appraiser has appraised the property assuming the property is held in Fee Simple title" or something to that effect. Then reference the engagement letter, and put a copy in the addendum of the report.
Not sure if I answered your question, but this is how I have been handling these requests.