instead of starting a completely new site why not contribute your time to expanding an existing site? Velobase for example. also why not make everyone a historian? get everyone to offer a model of bike they would volunteer to disassemble the bike and take all the measurements you like. chances are alot of these guys already know as much about they favorite frame then the builder did when he built it.

if I for example was disassembling one of my bikes to overhaul it and knew someone was looking for information on the frame demsions other than what the manufacturer supplied. things like the exact thickness of the dropout or the seat cluster to the housing stop support to the brake bridge I might be enclined to record it and send it off.