Very nice tutorial, I see many things that I can improve in my building skills

I also don't agree about "unnecessary cornering", there's nothing easier as going straight (with little slides) with any car. The more corners (turns) race has, the better it is

(imo)
About alternate route, many people are used to drive thru default ways, they are afraid of possible alternate ways because of big chance of failing there. And there aren't many possible alternate ways that could work out...
Also, I respect your wish that we should use all vehicles, not just fast cars and bikes, but, for example, when I made a Jetmax race (it was a good one), admin asked people add/del, and most of them said del, just because people hates boat (and flying) races... It's little unfair to let the players decide which race is gonna be added and which not.