i must say that on the right car they can look cool, i had single wiper on my mk2 and mk3 gti's and i liked em, however i really dont think the leon will suit it, i think they tend to suit little motors like your golfs and corsas etc
 
My previous zx volcane had single wiper as standard and the wiper arm was parked to one side. depends whether you could incorprate the motor/mechanism around the central hole. mechanism worked faster than two blade setup as has the whole screen to wipe. Saved me a fortune in wipers as you buy in packs of two but only need one....lol

agree it would look pants if when parked the blade was vertical down the screen but that would be down to the lack of effort converting the mechanism - queue ZX as screen would be a similar size, hence use the wiper arm and mechanism, may even be able to use the plastic surround between screen and bonnet and then would not have a hole where previous arm of the two blade set up used to protrude - all supersition of course and would need a visit to friendly scrap yard to try out parts for size...
 
Well we've established dan don't like it sooo... Swiftly moving on I personally think it could look ok but wanted to see if anyone else had done it.

I think it will be different and it'd a small mod with a big difference but I won't be spending a fortune on it you all know how tight my purse strings are drawn ;) :p lol