I just ordered Chop Source’s “basic” frame jig kit. Essentially I’ll have what’s shown in the photo, minus the center cradle supports and transverse legs. The center part I really don’t need, and I have enough spare stock to fab up some adjustable feet for it. The Chop Source kit is foolproof, precise, and can be easily reconfigured or disassembled for storage. You can start with the basics and add stuff like the rotisserie later. It has lots of nice extra touches, such as the diamond-shaped measuring points on the side plates.
The grand total for the kit plus 15 feet of 11 ga. 3″x2″ square tube, procured locally, was $327 after shipping and sales tax.
I should probably lose the “budget” part of the project description now.