Need a global item vault, especially when an army kills an enemy and the items they are awarded just disappear.

I want to capture my enemies' vault and take their goodies.  It would be a great thing to have built into the founding city automatically or as a tech that can only be built in your capital. 

"You have conquered Lord Markinn and the people of Gilden... your troops discover a vault in the Keep containing:  [insert item(s)]"

Yes, what heavenfall said.  And, a vault, like MoM, might be somehting built after much research?  - but not a standard part of the start game.

There needs to be someway to transport items between heroes without having to walk them to each other. Self evident really, simply to avoid the potentially severe nuisance factor. Of course there should also be some sort of cost for this.

I like the idea of a magic item vault like MoM. However I also like the idea of it being a unique building (ie only 1 per faction) which has to be built, probably with relatively low tech requirements and possibly some other benefits to make it fairly much a no brainer to build once you have the tech so long as you can spare the build time. I say this because the cost of transporting the items will already be somewhat self balancing, if you make the vault building hard to build AND have it cost to transport items then no one will bother building it.

And of course that opens up the possibility that if you lose the city with the magic item vault building then you lose your magic items...

Is say: vault nay,  spell yay.

I don't want more buttons and stuff and thingies, so I'm kind of hesitant to agree that we should add one.

MoM and FE are different games too. There are far more, far less awesome items in FE. In MoM I might have thought "This item NEEDS to go on my ranger" or whatever. In FE I'm like "Meh, that might be incrementally more useful than what he already had. I'll get it to him next time we meet." The instant need just isn't there, so this feature is not as valuable here as it was in MoM.

Remember, this is going to require another UI change, along with another screen/menu. It's may require adding additional functions to get access to data that's not currently available at a global level. It's going to be another thing new players are going to have to understand. Even if it's not a complex system, it is another system which is overwhelming when you don't understand the game yet.

So it's a question of resources and clutter. Do we need another mechanic that adds to the complexity of the game? Does it provide enough of a benefit to dedicate resources to implementing? For the benefit of cutting down on a bit of micro (not that much, in my opinion), my answer is becoming a more resounding "no" the more I think about it.

EDIT: The disappearing items is an important issue still though. If there isn't a cleaner way to solve this problem, I'll support this feature.

Winning a battle vs monsters without any champions, I believe.

No to a global vault.

Yes to a spell for transporting items (including those obtained by championless armies) at an appropriate mana cost.

You could make it so that Championless picked up items are always transported to the vault, and Champions can pay mana (like in AoW) to transfer items between any allied champion or sovereign, based on distance and power of the transported item.  Note I am not necessarily saying that it should also allow trade between allies, though that obviously is a possibility especially if FE gets multiplayer.

Depends on your definition of complexity of the game. If you mean complexity of coding and development then yes an item vault is undoubtedly more work than doing nothing from the current state.

But from a game playability point of view adding an item vault is likely to make it less complex by making the game easier to play and reducing micro. 

Like everything there will be a cost benefit analysis for Stardock to perform on whether the feature is worth doing.

I disagree. Multiple ways of doing things does not equal complexity. For example having only one difficult or obscure way of doing something is much worse than having two easy and comlementary ways to do something. I'm not saying that my example describes the item vault situation perfectly but I see elements of it.

I also think making something take less clicks generally tends to make it less complex but it is quite possible to design counter examples.