Gunter reefing systems

Imagine a short tube (couple of inches in height) that goes round the mast and which can slide up and down the upper half of it, but with a fitting on the mast to stop it going lower than a certain height which we'll call the limiter, so the limiter determines the lowest height the gaff can be held at when reefed (which would be about as low as the gaff can go anyway without getting in the way of the boom and the bundled up reefed part of the sail). Now imagine a fitting on the gaff that hooks into a loop on the ring just like the end of a spinnaker pole clipping onto a ring on the corner of a sail - you'd swing the gaff up and clip it to the ring just by pulling the thin string running from the bottom of the gaff up to its hook to open up the hook, then let go the string to lock it on. To get it right up against the mast there should actually be two hooks and two loops, one to either side of the tube.

The halyard would attach in the normal way just above this new hook part on the gaff and go straight up to the pulley in the top of the mast, so it simply pulls the gaff (already vertical) straight up as far as you want it to go, but it's the tube that holds the middle of the gaff against to the mast and not the halyard, while the tube is also free to rotate. You'd be able to reef easily all the way down to the limiter. The big advantage of this is that the ring has no need of a halyard and never needs to be tightened or slackened off - it just sits there independently. This involves the minimum complexity and maximum utility.

This system also adds to safety by ensuring that it would take more than one thing to snap for the gaff to break free, and even if both rings failed it would still be held high by the halyard - one of the excuses for switching to the Bermudan mast was safety, and another was easier reefing, but this eliminates the danger and makes reefing easy too. With rotation of the tube maintaining better gaff alignment, there may also be no performance deficit, aided by more careful shaping of the bottom half of the gaff.

Another thing I'd do is redesign the lacing system for the lower part of the sail so that there are independent loops for each eyelet which can be disconnected and reconnected with quick-release mechanisms, and perhaps these would just stay on the mast. Maybe they could be solid rings going round the mast, though I can't remember if any would have to get over the spinnaker pole attachment ring - if so, the upper one(s) needn't be complete rings, but could still go round the mast far enough not to pull off.

Toby, I assume you've browsed all the references to "reefing" on the forum (I get 3 pages of hits).
My solution is similar to the duckworks set-up in that diagram. I tie a line to the halyard strap on the gaff and shackle a small block onto the other side of the halyard strap. The line is passed around the mast, through the block and down to a cleat on the bulkhead below the mast step. When I slacken off the halyard to reef the sail, that line goes slack as the gaff comes down. When the gaff has reached the desired (lower) position, I pull the line tight to pull the gaff firmly against the mast. The sail is rolled around the boom.
As I wrote in one of the other threads on the subject, I do not consider a vang to be necessary when the sail is reefed, as one no longer needs maximum sail efficiency when there is too much wind. When you sail close-hauled as shown in the video clip, the mainsheet pulls the sail fairly flat anyway.