but I'd like to see them bring in time penalties for running a section when others can ride it
That's absolutely impossible to enforce, simple as that!
If it was like DH with riders going one at a time then you could maybe do it, but not a chance with 200+ riders at once.
So… first lap, 50 riders come into the first descent.
-Riders 1-30 get through cleanly,
-rider 31 dabs but gets through,
-rider 32, who is actually Steve Peat, crashes due to rider 31s ineptitude, he can't remount/it's not worth the time losses, so he runs down,
-riders 33-40 run down, having been held up by Steve Peat,
-riders 40-50 have waited at the top, then manage to ride down at the back of the group more slowly than those who ran
Who gets penalised, and by how much?