Hey Tim - I looked through my copy of "The Nature of Boats" Dave Gerr and did not find anything on DIY lazy jacks. However as per the happy hour discussion, your plan seemed very practical.
Thanks Brian. The book is available on Amazon, and I might order a copy anyway, as I've heard it's very good. I'm going to continue to suss out the design, see what actually works and what doesn't. I'll share what I find once I get a system together that is functional and practical for trailer sailing.
Have a look at Sail Control System, US patent 5,327,842 dated July 12, 1994. Patents can be adapted for personal use; just don't go into business with it.
Make note of the way these lazy jacks can be taken down and stored along the boom (Figure 5 of the patent). This is useful so they can raised when needed and they don't flap around against the sail and disrupt laminar flow. It's also beneficial that they can be stored under the sail cover. Hanging the upper blocks on the spreader arms about 6 inches from the mast seems to work better than attaching the blocks to the mast.
Thanks JGrahamK, I'll look that up. The approach I'm leaning towards at the moment is loosely based on the Harken design for boats 21'-28'. It will do all the things you mention, plus be easy to stow for trailering.