I suspect some of my fellow control freaks might balk at your suggestion, but I really like the idea of having mechanics that reflect the limits of low-tech communication. Requiring advanced magic and/or special items for long-range communication would at the very least make for some strong differences between the early, middle and late game that had little or nothing to do with whether you'd played as a turtler or started conquering from the git-go.

Quests and tactical combat that do not include the channeler might be a problem for something like this, though. How would you see a limited communication system affecting a champion leading an attack orce or sent questing to a distant locale? It'd be no big deal if any tactical engagements where the channeler was not present are required to auto-resolve, but I haven't seen any suggestions that things will work that way.

I think I have to say this is impossible.  Ok it's possible but just will not work for this game. 

1: If you have this limitation then it would seem odd to have the ability you have to have instantaneous feedback of what is going on in the world.  A camp on the outskirts of your land is attacked, in the game you will know as soon as it happens, realisticly you wouldn't know till the raiders have moved on or possibly never know. That would be EXTREMELY hard to represent on a map.  How frustrating would it be to have the map under a consistant 95% fog-of-war coverage and how would you keep track of the times of every piece of map that's been updated.  You can send scouts, but you have to wait for them to get back...if they do.  So  much time would just be spent on getting information on what is happening and then you would have to make descisions on your best information.  Not even being sure that information is current enough to make a good descision with.  This would also be hard to program in the enemy AI balancing 'scout' information with strategy.

2: I doubt that this game is going to have every event on a realalistic 1:1 time with each and every other event.  So a 'realistic' addition such as this would not fit since it's unlikely everything else is going to be on a realistic ratio.

3: Just doesn't sound like a fun mechanic to work with IMO.  I think there are much better ways to add sabotage and the-like to the game.

I want basic communication to be instantaneous. So, for example, my channeler can be aware of anything that isn't under fog of war (by communicating with subordinates or whatnot), and diplomacy could be done easily. However, things like trade or gifts would require caravans to set out, unless a substantial effort is made to teleport them (which shouldn't be common - really only for the most valuable goods or artifacts, or if the need is urgent enough). That said teleporting small quantities of goods could be a little cheaper than teleporting things like armies (even small armies) - having a channeler on each end could make it much easier than a channeler sending something very far away with no associate at the destination to help.

Trust the pigeonSquared to come out swinging promptly upon his return. The brilliant idea of channelers cooperating for a teleport spell opens up a slew of possibilites for long-term efforts like a Bifrost Bridge between capitals and even short-term alliances to do something like raise a volcano under a common enemy's capital or take down an offending overland enchantment. The teleport question itself also brings us back to just how much spellcasting, if any, champion units will be able to manage. At least some mage champions should be able to do something to help their channeler send reinforcements, no?

Yea, but the 'universal' magic mirrors in MoM were as much about limited dev time and limited PC power as anything else. I'd love to see big variety in how each faction implements communication magic, and I don't just mean different frames for everybodys' mirrors. I'm thinking about mirrors for some, pools of water for others, cups of blood, talking skulls/skeletons, etc.

On the item moving thing, I think mixing teleports and caravan delivery would definitely make for interesting choices, at least during those times when you aren't storing much mana each turn. If I know it will take a long while to get the necessary mana, should I leave that great find 'out there' until I can bring it home magically (quickly) or can I risk sending it with a caravan that might be captured en route?