If I had only a year to break the man-powered land speed record I wouldn’t develop a whole new machine.
I’d take the best cyclist I could get and seat him on the fastest racing cycle I could find, as comfortably as possible.
Then I’d assemble a shell around him using oasis plant watering bricks. This would be very crude to start with but it’s sufficiently soft stuff to allow a really streamlined shape to be sculpted that weighs almost nothing. The critical element in reaching top speeds is the form drag -given a tight timescale I’d minimise wind resistance and forget the other details.
I’d also supply a leaning pad for the rider’s chest so that he could relax as much as possible (no need to steer in this record attempt).
The other critical aspect is to allow the ‘engine’ to breathe effectively. I’d run the record attempt somewhere at low altitude with lots of trees around for oxygenation.
I’d also cut a few discreet slots in top side of the oasis shell to ensure no buildup of carbon dioxide.