The one obstacle I would like to see is a car wall like the ones used in the Mr. Destruction stunts.
If I was in charge of designing the WF racing course I'd have the drivers loop around funboxes halfway through the straightaway, then speed to the final turn and make the jump. As it stands, I think that the one turn at the end is unsafe and boring.
For freestyle, I think it would be cool if dump trucks brought in different soils from different venues that Monster Jam went to. It'd add variety and it'd look cool too. Maybe some water could be sprayed in the middle to make some mud. xP. In terms of obstacles, I'd have a long double on one side with a ramp to launch over it near the turn, but no other dirt ramps on the double stacks. There would be a rock wall on the other side of the center FMX ramp instead of a dirt step up. On the opposite side of the double there could be a very steep ramp facing the opposite sideline consisting of two school buses, one on its and one upright. In the middle of the course there would be a long tabletop which extends to the 50 yard line where campers and other breakable objects could be placed. The scoreboard end zone side would have a shipping container positioned parallel to the tabletop in the center and filled with dirt. Crush cars would sit on either side of the container and scaffolding would be placed on top. The empty spaces on the track could be filled with vehicles as the night progresses.