I have thought about it, as I'm sure others have, but other than manual timing yourself with a stopwatch or something you can't shift the timing points set in the game.
Honestly I think it's a little dangerous because anyone who's only gone round the Ring in GT will then head to the Ring for the first time and think he/she needs to fly through the lining up area and gates as fast a possible after the last corner instead of letting off the throttle/gas at gantry.