Mixed race armies and battles

[Makrangoncias]

Probably not I'm the only one who'd like to see battles with mixed armies. Dwarven infantry holding the line, elf archer striking from above, while bretonnian cavalry riding down the enemy.

Or the other side, beastmen fighting alongside chaos chosens, supplied with demonic forces.

It's so sad that it really rarely happens that you can actually fight alongside your ally in deciding battles but it would look so awesome.

I don't know if it's possible but I guess it should be to make a mod that adds a new diplomacy option after military allies (let's call it "share arms") that would let you recruit your allies troops into your own armies in your allies' territory. For example while fighting the orcs with the Empire it would make so much sense that you can replenish you fallen units with fresh dwarven troops.

Of course there could be limiting mechanics just like in tabletop you suffer penalties if you recruit units out of your league (If you somehow manage to ally with orcs or undead while playing with the Empire both units suffer leaderships penalty) . Sorry I'm more familiar with 40k rules but I guess there is something similar in fantasy warhammer.
Or you can only have like 40% foreign units in your army or they start to suffer leadership penalty and possibly desertion.

Also gifting or receiving armies to and from your allies would be nice but that's probably much harder to achieve (just like trading settlements, that would also make a lot of sense)

[Chibbity]

I don't think mixing units within armies is a good idea.

Letting our AI allies temporarily grant us command of one of their armies would be nice though.

I find the War co-ordination target to be a little akward to use as the computer takes forever to get around to actually doing anything about it, and once it does it's likely the target has moved off or is dead.

[MrMurLock]

I'd love this idea to be implemented on skirmish / custom games!
Campaigns would be too burdensome and dilute the flavor of each faction, but I see it as perfectly legitimate for a custom game to have mixed unit armies.

[Makrangoncias]

I think with the right amount of constraints it would be a nice addition to the campaign too. Yes, I don't want it to take away the uniqeness of each faction but playing the 50th battle with the same boring swordsman unit I'd really love to see some more interesting units.
I'm playing with radious that also expands the options for army setup, but still... I'd really love to see some other races especially if we are considered bulwarks of civilization.

The temporary command would be possible in my opinion if there would be a "crusade" mechanics implemented, each army that is commited to the crusade can be controlled by the player.