Allies taking empty cites. (Remove/Change)

I have nothing against it, and I know the purpose (total annihilation games). But many a game have been lost because my ally doesn't declare war on me, but takes all my empty cites. I can't declare war on him or I'd be destroyed very quickly. Thus he causes my economy dies, and I lose the game. I find it ridiculous that ALLIES can steal all your cities. I think there should be some sort of in-game request to inhabit a city while the other ally retains control of the city. (Original city owner). This goes along with an idea I heard about allies mixing stacks to help defend a capital. Either that allies can only take an allies city in an total annihilation game.

Why not leave a militia in each of your cities instead?

Yeah honestly. If you're leaving 0 in your cities, it means you're either GW or Blitzkrieg, so at most militia cost 30 creds.

Don't leave your cities empty.

you get free militia when you take a city learn to not leave any empty cities

Alternative solution: Play Iron Fist.