Thats easily sorted - you put a capacitor in the system with a 50 second buffer. A lot of hub dynamo lights have this capability already.
Boycey - I hear what you're saying about sales. At some point we will go to integrated lights on utility bikes - It may depend on when the public demand them or (IMHO more likely) when BIKE INC deciedes to drop this science on us - but it will happen, its a question of 'when' not 'if'. In 1980 there was no demand for an aluminium framed commuter ...but crucially there was no supply either. Taiwan is very good at coming up with supply and as soon as they do demand seems to follow.
The more I think of it - all that wasted space inside frame tubes - whole sections could be used for other things; what about the seat tube being an integrated pump chamber and the saddle the piston to compress - hole on the back of the seat tube to attach a flexible hose and you never need carry a pump again. A section of the downtube could be used to house a gel battery charged up by my BB mounted dynamo, tools in another section...