Can't you just shift through the gears with the H Gate never even pressing the clutch and never letting go of the gas?
It seems to me that would be far more needing of the fix than no lift gear shifting...
It depends on the car. That works, for example, with the SLS and the R35 GTR.
For most cars, as soon as you press the clutch, you cannot engage a new gear without using the clutch and releasing the throttle first. With the SLS
et al., pressing the clutch does not invoke this behaviour. I've not tested driving a "normal" car without touching the clutch yet (can't help myself), though - it may well be possible, but it won't shift any faster than ordinary shifting in the game anyway, so it's not an advantage.
Second gear is a proper bitch, though. You have to really deliberately take it slowly in order for it to "engage," and the throttle had best be completely off, else you're buggered. The other gears do not have such a stringent minimum time (between engaging the clutch and selecting the gear) to adhere to. Annoyingly, once you miss, it seems that you still have to engage 2nd gear slowly, which is where I keep going wrong!
I think it's more to balance standing starts, since second gear
tends to be considerably taller than first (relative to the other sequential-gear pairs) so the advantage of just jamming it in and letting the clutch take up the slack is greater from 1st to 2nd than from 2nd to 3rd, etc. Flat-shifting is disallowed in general, assuming you use the clutch.
So, the fix then would be to add in a check for which gear the player was last in before trying to select 2nd, and only disallowing a fast engagement if that last gear was 1st. This is probably what is hacking off all the drifters, since going from 3rd to 2nd quickly is also being penalised (perhaps - I know that 2nd has been difficult for me at times, but my heel-toe action is pretty lethargic, so it tends to delay engagement for me.)