Enough 6 by 8 gateways could transport all the food, equipment, and weapons an army would need on a campaign. Big war machines and siege weapons would generally be broken down for transport however they were moved(gateway or traditional), or an army would make them after they reached their destination.



The Seanchan recently captured between 400 and 500 trained Shaido channelers, even if only 1 in 4 can create a gateway, there is your 100 Damane. Cavalry can be led through. With a bit of practice they could become quite proficient in moving large numbers of mounted soldiers in an efficient manner.



This is a good example of why linking would not be necessary for moving a large army. 2 individual channels could move a group of 5000 people. This group would include mounted cavalry and carts. They did not merely do this once but multiple times over several weeks time. Now consider how much a group of 100 channels who can make gateways transport.

With plenty of carts and narrow wagons and a whole lot of military and Seanchan discipline and organization, the Seanchan could move a well supplied and large army anywhere they wish.