I've been playing with this as well since i have connections with 6/1, 10/1, 30/2 and 100/8 speeds, all together in the same pfSense box. I'm starting to think the only way to achieve this is to create 1 VM for each wan link, with it's own pfsense and within them make the up/down limiting with the last box just doing all the current traffic. I really don't like that solution.