Right now, teleportation is an easy mode button. Even if the AI somehow manages to get an army together AND somehow manages to bring it near your city AND you have no units anywhere nearby, you can easily teleport your sovereign's army, or imbue the champion leading your army and have him do it (or have him return to your capital, have your sov return there, and THEN teleport the whole shebang). 

It's goofy. Too much ability to consolidate forces, it makes a strategic reserve and minimal frontier defenses the only doctrine necessary.

So here's what I'd like to do!

You click teleport and select a destination and your army is dumped in the middle of a map. There's a chance that demonic enemies will be on the map, or loot, or both. There's also a chance that your units will take damage or be healed on entering. 

The map is pretty good sized, and there are a fairly large number of exits, but they're all about three turns away. That's real game turns, as in you can continue playing the main game while this is going on, and swap to your character by clicking the portrait. The number of exits is also bounded by how high the teleporting character's intelligence is. The smarter they are, the fewer the exits and the greater the likelihood that any given exit is correct.

If you pick a correct exit, you get dropped out at your destination none the worse for wear. If you pick the wrong exit, well, you get dropped at a random location somewhere near it and take a small amount of damage. The higher your character's intelligence, the lower the margin of error and the lower the damage. 

This system would:

Make teleport costly in terms of time. No immediate reinforcements means players are forced to defend their borders with troops rather than a magical warping army of doom

Make magic a little scarier

Make teleport more interesting for players (your magical journey is a quest in disguise!)

Be really weird

edit: When you get right down to it, players remember the quirks of a game more than the actual mechanics. I can't tell you a thing about one of my starcraft games, but I know right off the bat what the silly phrases were for a bunch of the units. This would add some flavor and make the experience of actually playing elemental more memorable