The SP would have been bigger if they didnt have to redo everything. The only 2 maps left in from orriginal development was the boat map, and the AC130 gunship. If i remember right from the director commentary, Al-Asad was planned to be on that boat level, and at the end he escapes on a small boat, at which point the SAS are ment to follow him and there was a level planned where you chase him across a beach or something.
All of that was changed in the end though, and i bet it was all these messing around with changing the storyline that limited how much time they had to develop levels.