Thanks for the very interesting chart! The general concept of the 4C gearbox appears to be similar to the one in my 1.4 Giulietta, albeit 6th seems to be even lower. At 3000 rpm in 6th my G is at 120 km/h, whereas the 4C is as high as 142! Looks like it's mostly meant for eco-cruising on the motorway.
The severe rpm drop between 1st and 2nd if you redline it is also roughly the same as in the Giulietta. Doing takeoffs in a hurry (with a manual) takes a bit of practice and is actually pretty difficult with a heavily loaded driveline.
Looks like the 4C would have been a pretty tricky ride with a manual.