Hi,
sorry for chiming in without a real contribution (I haven't had time yet to read the whole thread). But given that snapping is a common issue with tech drawing and CAD, I was considering to include some of it in my GSoC proposal as more advanced features. In particular, "tangent snapping" (of lines to curves, possibly even of arbitrary curves to each other) would be very nice and seams quite feasible using 2geom.
Since I know that Diederik is working on snapping and I don't want to steal his work :), my question is mainly directed at him: Do you think this is a good idea? If so, what else would you consider worthwhile (and don't want to do yourself)?
I'd also be very interested in user feedback on this and on tech drawing in general. As suggested by Bryce, I'm going to set up a blueprint on LaunchPad so that people can contribute ideas directly. Later I'm going to extract a suitable subset of it for my refined proposal. It may take a while before I get to it, though (graduation exams are looming :-/ ).
Thanks to all, Max
P.S.: I saw that this thread originally started on inkscape-user. Feel free to forward it there. I'm not subscribed to this list, though, (and won't be for the near future) so please include me directly in any replies if you want me to read them (I'll try to respond in this case but as I said time is sparse currently so please bear with me if reply is not immediate).