One little detail that's missing from the final (no turning back) point when doing a scenario is choosing your gearbox. Manual or Automatic. I'd find it that much more interesting.
Can't you simply press A to switch gearboxes ? Or set whichever one you prefer as default ? I'd find it annoying if i had to press what i want multiple times.
Gearbox mode is for swapping between realistic and arcade modes, and I think the OP is asking for ability to actually select the kind of transmission you may want. Such as switching between 4 speed auto, 5 speed manual etc.
Oh, that might not be a bad idea then but i'd prefer having the gearbox that should come with the car anyways.
often part of the difficulty involves using the assigned transmission (for example, police cars are often a pain to drive with the auto box, but that's how most RL cars are) so you have to put up with it. if you simply don't want to drive manual for whatever reason, then just use the arcade gearbox mode.