Can 当作 ever be used with a direct object behind it? If you look up 当作 it says something like 'treat as, regard as, look upon', however, from what I can see, it only gets used in combination with 把 or 被。
Is this 把 a word with meaning, or a particle?

Is it at all possible, lets say, to rewrite 

别把我当作外人。 with the form '当作我‘ and not use '把’？ Maybe '别当做我为外人。‘

Don't treat me as an outsider.
No you cannot do that.

Please always use 把 or 被.

把: take

被: be taken as

别把我当作外人: 
Don't take me as an outsider

我被当做了外人: 
I'm taken as an outsider