Latest update on this episode (nonrelevant to the US context):
It seems like this 500% rights idea won't take place after all. Apparently in Singapore, the rights of the commissioned portrait goes to the portrait commissioners,
NOT to the portrait artists. The Intellectual Property Office of Singapore mandates this in term copyright clauses found on their website here.
http://www.ipos.gov.sg/leftNav/cop/O...and+Rights.htm
My client has reverted with her lawyer's revamped clauses, and hopes that i'd include it in the contract. For now i can only submit suggestions for provisions in the interpretations of the laws at hand...