diesel engine have high torque but limited by low rpm. They can benefit from such gear box. Just need to be sturdy though

why not 100sp? is there a trade off ?

Doesn't matter anyway since the Genesis gems won't be available here at all (you heard it, the COE woes)

10 or more is ok, as long as you don't have to manually shift it.

Modern gearbox upshift very fast to save fuel,my Z 7 speeds auto can upshift to 7th gear in just 75 km/h....

its easy if u tink of it as a mountain bike with 18 speeds. most of the time, u skip gears like 2,3,4,5 - 7,8,9,10,11 - 13,14,15,16,17

so if u enough leg power, its something like from gear 1, u change to gear 6 and then gear 18. the remaining gears are totally redundant

For the 51% of people that live in the city vs 49% that don't it seems to be that you do need ten gears. Ten gears would only go to fuel efficiency not speed. In a manual transmission the final gear is almost always 1:1 Automatic is around 0.75:1. The plethora of gears prevents the "city dwelling bumper riders" from burning to much fuel. As for the 49% that live along the "long open highway" they concentrate more on how they drive then what they drive, its far more effective.

As far as the Autobahn goes, a car with a 5.9L NASCAR engine will perform nearly the same with a 4 speed as a 6.