The trimming of L7 was for scope reasons, to make the workload more manageable for the artists.
I scripted and designed all of the missions, though programmers of course were heavily involved in prototyping and game up with some core gameplay ideas and functions (e.g. "knock things out of the car").
What I do remember was spending a lot of time tweaking and tuning the missions in the later levels - as the difficulty curve rises, there is little margin for error. My friend Richard Mul was also a great help there; before this he was on the Black Box (EA Downtown) team that produced a great Need for Speed revival on the PS2. His experience was invaluable in the final difficulty tuning tweaks. Sadly, he passed away not long after the game shipped.