You don't fully understand the purpose of Natal if you think that it would be better to replace some of the actions with a controller of some sort (such as a buzzer, steering wheel, etc).
Basically in your OP you use the Wii as an example of how some people grow tired of the motion controls and wish they had a traditional controller. Well, guess what, the Wii still sells amazing and hasn't worn off yet. If Natal is good and has good software, neither will it.
Also, Natal is targeted at the 60% of households that don't own any console yet, that means this targets people that not even the Wii has yet.







