I'm sorry to bring this up again, I just like this idea so much, I just wish it would be implemented in the next patch:
Now that holding the shift-button down isn't declutching anymore, I thought of another way how you could implement a manually start: When a race is started, you're standing on the grid in neutral with handbrake on (so only difference to now would be the gear), and as you shift to first the handbrake turns off (as it is now already)... This way you would prevent rolling before the start, wouldn't you?
Another thing (maybe a bit easier to implement): When exiting the pits, the engine should be OFF, and you should have to start it for yourself (don't even bother to say "nK", I had this idea even before the release date of it was announced)...