FPSC wasn't build to take levels from different applications. TGC only had to worry about relatively small items for collisions, until we came along. The collisions are more or less based on one segment size only, ot was never intended to be stretched beyond that. Items & segments larger then the 1 fpsc square are a potential problem in regards to collsions.
Using larger collision schemes, means a larger demand on your system, means FPSC will even run slower on your system. Keeping the collision for small areas only is very fast. TGC couldn't even add it if they wanted too, it would slow down FPSC even more, create more angry customers and so on.
I'm pretty sure in the future TGC will sort this problem out, since the demand for this is great, as well as the demand for outside levels. So one day they'll have to do something about it. But it will not be before the speed issues have been dealt with and perhaps now even in v1.x.