A twist on an old idea

[Fate]

I think that it might be interesting to have an almost "barter"-esque table. Where I could maybe rent out units like mercenaries (appears in a buyer's province and reutrns to me after 3 months or some such). Agreements on moving through each other's terrain, mutual attacking, maybe even allowing my opponent to take resources from my provinces w/ a fort. Or gem donation, item donation, and gold donation. I think that that would cover most all the possibilities. And maybe if I give away some armies and am conquered before their return they become real mercenaries.

I know that this is probably too much and a small thing compared to others, but it would be sorta nice.

[magnate]

I think the important gameplay issue to solve is allowing two allied armies to fight an enemy army *together*. I don't particularly mind whether you have a straightforward MoO-type diplomacy system or some kind of vassalage/pantheon system, but the whole point of being able to work together is to defeat people you couldn't defeat on your own. Sequential attacks on a powerful enemy are a lot less effective than attacking together. In fact now I come to think of it why limit the design to two allied armies ... a certain famous Middle Earth battle comes to mind ...