A lightweight bike would be nice

A decent target.

Sub 7Kg could be done without sacrificing stiffness, and without buying some of the silly money weight weenie components.

I also feel (IMHO etc.) that if you get the stiffness right. Such a bike would feel far lighter.

Frame = Dolan Seta
http://www.dolan-bikes.com/track-bikes/frame-sets-track/dolan-seta-framesets

I already have the frame and fork (Principia track from chainreactioncycles.com). So no need to spend on those. I am pretty sure the damn thing is stiff as hell. At least that's the usual word on alloy Principia frames.