Oh please, controlling throttle, brakes and the clutch is second nature to anyone who drives a manual car (or has enough time in LFS doing the same). Don't try to tell me that you have to actually think "OK I'm spinning... I should push the clutch in! Left foot go down now!" I suppose that my argument works best for people who don't use their feet to control throttle.
Also when you spin you push the clutch in and release the throttle, right? The auto-clutch does what you do instinctively, but of its own accord. I might drop the clutch sooner coming out of the spin if I had a clutch pedal compared to how long it takes the auto-clutch to do the same task. This can also cause some heat issues.
Is overheating the clutch in race conditions really an issue for you? Or is it something you're just bringing up that doesn't really have any bearing on 99% of the races you run in?
I understand that LFS is a sim, but some people are taking it too far. No matter what you call it, it is still a video game played on a computer. Realism to the point of excluding people who are less fortunate is more damaging than it is good for the game. Giving people the option to exclude such people on a whim seems very silly. I race with/against a mouse user who can beat me, but my first thought is not "wow he shouldn't be allowed to race with me, he doesn't even have analog throttle/brake input", it's "argh, I'll get him next time!!"
Some methods of input have slight advantages or disadvantages, more or less control, a few extra things to go wrong, but somehow it seems to be wheel users who are least surprising when they're competative, even with all their extra burdens they must carry with them. If I manage to beat a G25 user it's not because of some advantage (especially with my gamepad) I have, it's because I'm better than them (or maybe they had some accident ).