Think about it this way: if you had the same ratios, it'd pretty much be a fixed gear. If you had a taller gear for the "reverse" you could keep the pedal rpm's between the two different gears and slow down the pedals to engage the "reverse" freewheel.

However, with this setup there will always be noise coming from one of the freewheels. Imagine always hearing a freewheel clicking, even when cruising along pedaling perfect circles......kinda interesting though.....