I think for branch offices, the Enterprise licensing model that allows multiple scanning servers is something that could help. You would have a system local in each branch office doing the scanning. I don't believe there is a way to limit the amount of bandwidth per scan. The thread values will limit the number of concurrent scans (essentially limiting the max bandwidth). With your current thread values, worst case if you have setup scheduling that occurs simultaneously, would be 14 concurrent scans. Maybe you need to drop down to 2 and 2 (it would just affect the time to fully scan queued systems).