My design criteria probably don't match other's - but I'd be pleased to hear comments, advice, whatever...
1) light weight. I don't have a target weight, but as light as I can get it and still keep it rigid. I'd love for it to be under about 500 grams without a lens. Whether this is possible or not I don't yet know.
2) traditional looks and materials. Which means a timber body and slide-plate - probably cherrywood or black walnut - both of which are easily available, reasonably low density, dimensionally stable, don't release nasty oils or saps, and look good. However I'm not wedded to tradition; I'm perfectly happy to use carbon fibre - flat or circular bar CF is reasonably inexpensive, stable, and with a low coefficient of friction - or plastic rack/pinion focussing rails.
3) it's got to fold. No ifs, no buts. Size is important as well as weight.
4) it should be capable of construction by anyone who can put a balsa glider together - no special tools should be required. Where there are parts which need to be shaped, they should be supplied shaped; there are plenty of people out there who can provide dimensionally accurate CF and also accurate wood cutting. I have nothing against lasers. I don't want to have to buy a milling machine...
5) as a landscape photographer, I rarely if ever need movements other than vertically. I'm prepared to accept the limitation of no twist or slide.
6) I normally use a 135mm lens; this would be the default lens. It should focus to 90mm and also accept at least 240mm on the extension.
7) the front standard should tilt back up to 15 degrees and forward flat for folding; an index at 90 degrees is an obvious need. A vertical shift of approximately 40-50mm upwards is proposed; no downwards shift.

9) the back should be able to accept a standard dark slide (say Fidelity, since that's what I have!) in either orientation. It may require e.g. a thumbscrew change to alter this.
10) this should be attainable for under five hundred quid; hopefully a lot less. I'm a poor man, and currently unemployed...
Any thoughts?
Neil
p.s. Cameleon appears to have stalled; Bulldog is available but doesn't fold; Bender appears to have fallen by the wayside...