Not sure if this has been mentioned, but what about a Portal/Portal Mark spell!
Kinda like teleport your party spell, but this one creates a portal that last a minute or so and is reversible.
While the portal is open people may pass through. When you reopen (after cool=down) it lead back to where last cast it.
This way you can create a portal to the marked destination and back again.
Such a spell would allow you to move an entire army quickly.
-
Another spell that would work similar and be a similar portal type spell, one that is locked to a gate you have somewhere. Also (preferably) this "somewhere" isn't part of the normal map.
It's a small area, you could think of it as in between worlds.
In this small area you have nice big house you can go to, store stuff, sleep, etc..
The idea is based of the "Septim's Manor" (I think that's what it was called) spell/mod from TES: Oblivion.
You could call this spell "Drastikos' Manor" if you like.