As for now NFS seems not to be a preformance killer - right now all the templates and other static files are on NFS server and it seems to work very well. I'm not sure how it will look like heavier traffic on NFS...
Your idea with mixing dynamic and static content with Frames or Layers seems to be interesting and I already see some places where it can by deployed.
Obviously I'll also take a look on some caching scheme befeore going completly to static