There are a few things I find unclear about the Battlehosts book in terms of building an army and mixing it with non-battlehost formations.

So you can ignore the ratio of common/rare formations in a battlehost and you can use a hero from the formation as you Leader.
But do you still need your single common formation as per the WotR rulebook?

I'd assume that if you had an army consisting of just Battlehosts then you wouldn't need the common formation. But what if you have an army that uses the normal formation selections and also includes a Battlehost?

When Battlehosts came out I wrote a 1000 point list that consists of the Army of the Dead battlehost and the Three Hunters.
I look at it and am thinking that I can't actually have Aragorn as my Leader because he's technically from an Allied list and I'd need to have 1 common formation to make the army actually legal...

Thoughts?