Jarkie:
LabVIEW (on any target) will not try to load or execute any VISA functions until they appear in the flow of the diagram. So if you have a VI that includes VISA refnums but they are inside a case that never gets executed, then it should work fine because LabVIEW will ignore the VISA portion.
For what it's worth, the next version of NI-VISA will support FieldPoint. So if it's just long-term extensibility you want, VISA is the way to go. But if you need it there now, then your idea ought to work.
Dan Mondrik
Senior Software Engineer, NI-VISA
National Instruments