I am reasonably certain that MSA's are not assigned. That is a pilot only altitude that ensures obstruction clearance and does not pertain to ATC. In other words, it is the altitude the pilot derives from his/her sectional. MIA's are designed for off-route segments. i.e. if a pilot is not on an airway, it would be the lowest assignable altitude, it is the MSA for controllers. On the airway, it would be an MEA that that is used which ensures signal coverage and obstruction clearance. MVA's do NOT peratin to a VFR aircraft. MVA's are the lowest altitudes that an IFR aircraft can be vectored. So, to try to answer your question, if the aircraft departs and is not on an airway, it must be issued an altitude above the MIA. If the aircraft is VFR and is on an approach, I would assume it is a practice approach. Once you agree to give the practice approach, the aircraft is then treated as if it were IFR. At this point, the MVA must be used. It is also a precarious situation because VFR's are not normally given hard altitudes. They are expected to maintain VFR. Deviations high and low can be expected and seldom declined. That is the ARTCC take on it.

Maybe this helped a little?