I agree with gamegeek2, you've almost got stronger when becoming a horde.. In vanilla BI, I once tried a "bold" move with the Sarmatians of becoming a horde at the start of the game to move est and wipe out the faction living there... I sieged their only settlement, defeated them after a costly battle only to end up with one settlement, a depleted army and a whole horde of 5-6 stacks full of vengeful family members of the "defeated" faction that wipe me out in turn...

And if all your FM die, example during the siege of your last settlement, then you're done for! An important fact to know;p

But if it can be like a trump card for some faction facing annihilation, that could be a nice feature

cheers