You will get terrible collision problems, especially with the AI, as they hate walking on anything other than a proper segment floor in my experience.
You would really need to use the rolfy way and import the resulting mesh (or heightmap and use the terrain tool) along with an exported "supertexture" (I think it was called that last time I used T.Ed) into something like Max and use the slice tool to make loads of 100x100 sections of the terrain. Then place them all into FPSC one slice at a time.
That's just my opinion though.