Not sure if this has been suggested yet but I'd like to know whether people consider it likely or desirable.
One of the biggest issues the WE face is how to paint the map their colour given that they do not build and defend fortified settlements. I've heard a few suggestions on how to remedy this problem but haven't found any of them satisfactory.
There has been some speculation about how a new worldroots mechanic might serve this purpose. If the WE army could teleport to certain locations they could better position themselves to defend against threats on all sides of their empire. My problem with this is that it would need to be pretty OP in terms of cooldown and available destinations in order to be effective.
Here's my speculation: WE outposts could exist alongside allied settlements as a sort of positive undercity. They could otherwise function similarly to how they do now. With only one optional building slot and a small garrison. The small garrison could reinforce the allied garrison during a siege. Perhaps deploying outside of the gates or coming from the map's edges as if they had just come running from their forest outpost.