I'm kind of surprised that the software does not already do this. If you have an object on the bed which, with brim, exceeds the dimensions of the bed, why would the slicer still try to put material there?
https://dl.dropboxusercontent.com/u/863 ... e_area.jpg
I've had a few plates where s3d would happily print outside of the configured workspace.
Running Simplify3d 3.0.2