If there are not too many pulling the massive Exchange download at the same time, and assuming you can manage the bottleneck, it could be as simple as using fair queue. This would allow exchange to use all available bandwidth, but share it with other flows, i.e. Exchange wouldn't monopolize it. (You mention LLQ, if you're using CBWFQ, CBWFQ's default-class normally supports FQ.)
If you didn't want Exchange traffic to share the bandwidth, you could accomplish this with a traffic shaper or rate limiter.
Examples would be very dependent on the platform's feature set, version and hardware.