Further, I suspect that replacing the entire fllor of the car is overly invasive, and that there are more expedient methods.

Rob, I remember you posted pics and captions of the underchassis repair/welding on your E36. So, what you're saying (I'm getting confused with E36s, E46s and Z3s) is that you have the documentation for that procedure, but won't let anyone see it for fear of legal repercussions from BMW?