There were later aircraft- the Vickers Windsor for prime example- built to the same constructional method as the Wimpy, which was largely a failure, did not come close to its' predicted performance, and I wonder if the geodesic structure was the problem; that it was maybe a bit too flexible to push through the air at high speed?
Advantageous at two hundred knots, debatable at three hundred, liability at four hundred and up- simply too likely to deform with the airstream and throw up large, unpredictable amounts of drag and turbulence? Wouldn't swear to it without modelling it, but it smells right.
What was actually available at the time or in very near prospect? We're looking at the phoney war here, realising at some point between September 3, 1939 and May 10, 1940 that the Blenheim is not likely going to do very well at all, and anything picked is going to have to exist there and then, or be very easily kitbashed together.
How much faster would an Avro Anson go with standard Pegasus engines, 900hp or thereabouts, in place of the existing 350hp motors? Granted it is very, very un- fast to begin with, but it's not that lumpy- tilt the windscreen back a bit and it would look sleeker than the Blenheim.
Gloster Reaper would be ideal if it had actually made it past the prototype stage. Sufficient changes and yes, but not at the last minute. The reason, according to Wiki, is that despite it's promise it was ditched to free Gloster to concentrate on jet aircraft development; now is this an example of foresight that could have been done without? Is it worth trading a tactical bomber in 1940 for a V1 interceptor in 1944?
What about the allied, in- production Liore et Olivier 451? A good thirty miles an hour faster than the Blenheim with a better defensive armament and more than twice the bomb load, it is a generation ahead of the Blenheim and it shows.