I'm sure this has been submitted in the past but I wanted to bring it up again. A lot of people I've talked to recently have agreed that some cars would greatly benefit from the option to switch to manual transmission. I believe this and cruise control would be of great use. I just wanted to add another thought that is somewhat related as well. Everyone has their car preferences right. It's just unfortunate how some cars perform better than others no matter what. I believe that a system where people can truly upgrade their cars would be beneficial. I also believe the costs should stay relative to performance of course.
EG. You have a mustang but you want it to have the speed of a Lambo. Make it to where you can achieve those speeds but at a relative cost to the price of a Lambo.