ill get killed for saying this on a vintage post... could get tiagra crankset 4500 (2011) with hollowtec II - ive heard good things about it. I am a powerful rider so weight isnt an issue.
I've been looking at extra long breaks to fit 700c wheels - Alhonga do good ones that don't look cheap despite the name of the company (which does sound cheap). not sure about the wheels yet.

I dont particularly mind fitting new parts onto the old frame - these new parts are probably better than the originals fitted. Then again I want this bike to look tasteful too (no one will take me seriously with a tegra set?).

the leather seat and the clamp are good ideas...French fittings are weird.