I think, its a very good idea. Why should it be bad, if you can define a curve as a checkpoint?
In my view, your idea could be good sometimes. (how about a possibilty of choosing between boost or not boost after respawn in the editor?^^)
@zooz
Yeah, it could be hard to see, what friction or boost a block has, but it also has some good aspects.
(As I understand, it was ment like this: You can set the friction of a block, you created by yourself, not for every single block in the editor^^)
As an example for adjustable friction: Someone creates a mud-block. Now it would be nice to be able to set the friction of the block.)
And for the variable boost: You now these signs besides every boost? How about a numbers in this signs for telling the driver the boost...like 150%
Another option is just to allow 3 or 4 boost types with different colours. (green, yellow, red and...äähhh...pink

Sorry for my bad english
