Our FMS sets have no preloaded routes, no Rt2, and they don't work out intersections for you- it all has to be done manually. All these bells and whistles cost extra! One little thing I miss is being able to load a time into the fix page to have a little green circle telling you where you'll be at that time.
NATs are always loaded manually (except 777?) in the form 5130N for 51N 030W. A re-route is no more complicated than loading the tracks initially.