I know this is likely to be extremely complicated, but would it be possible to edit a cross sectional curve created in this way and have it affect the original model? I vaguely recall seeing something similar in SolidWorks once, and being impressed..

Also, to add to the debate above, a cross section tool similar to Sketch Up would be very useful for me. It would allow me to expose areas of a model for editing that are otherwise invisible (I'm using Moi for architectural work, so changing floor levels, adding doors, and so on.)