I like the idea and have thought about it - in fact you've answered my question about 'how do I keep the new rim in place until I've got enough spokes in it?'. Nonetheless I'm getting a bit impatient and have got a big ride coming up soon, and I can see a do-it-myself job dragging on over a couple of weekends by the time I include 'learning time' and the inevitable trip to the LBS for final truing when it's still not quite right.... So I think I'll have to keep that aside as a project and throw money at the problem for now.
Don't know if anyone has used
Rutland Cycling's online sales. Their 105 hub+Mavic open pro rear wheel is selling for £94, which compares well to the cost of a new rim + rebuild (£70 to £80 in all), plus which I get a brand new hub to replace my 10 year-old one (still in good working order though). This is the link :
http://www.rutlandcycling.com/23364...mano-105-Built-Onto-Mavic-Open-Pro---32H.html
If anyone's used them or has any feedback I'd be grateful to know.