My other car is a MINI!!!!
I looked into this a while ago, and didn't bother in the end.
The stock wiper motor would be modified to give you a single wiper activation I reckon, but it'd be fiddly.
Be clocking the drive arm round, you could get the wiper to part vertically up the screen, and give a reasonable sweep across on the standard length arm.
if you wanted full coverage and a larger sweep area, you could achieve this by shortening the actuating arm at the wiper end, as the shorter arm would give a greater sweep from a given motor input. This in theory could be made to park vertically or at the bottom depending on your preference.