Let’s come up with new “war machines.”

Yes, and you could also create a teleporter for a specific faction: it would be useful both for sieging a castle and in general combat – you mark a point, and then units can enter it and teleport. I'm not arguing, it's similar to the teleport spell, but this is for a single unit, while with a teleporter, everyone can use it. Also, you could add an ability to a hero's skill, so that when passing through it, they can, for example, get rid of negative magic or heal.