Hello Christopher,

I haven't used it but I know when I was looking to purchase Rhinoworks to add some parametric functionality to Rhino I ran across BriscCAD since the company that used to develop Rhinoworks currently concentrates on their core CAD product. It looks interesting as a 2D/3D hybrid modeler and is right under $1K to purchase, you might look into it as an option that at first glance seems to fit your basic requirements.