Of course they can be ranked, power is power- juubi, dna, training, skill, smarts, are all aspects of power ( who cares if it's inherited or not, next you'll say bipoler individuals cannot be ranked. In a vs match it doesnot matter how you get it,
If you want to be technical about "being a solo king" then sure Naruto, and all individuals with exterior help should be excluded as the definition of "solo". However, that is only a exclusive ranking, to say jinjuriki can't be ranked in general is absurd, they should only be excluded from "solo rankings".
In general, when being ranked characters get abilities/items that they usually have on them in the story. Batman would be base human without his technology-but when he is ranked he is always given his utility belt etc...
Biju should be treated like summons- since in the Naruto world summons count as part of ones arsenal and usual abilities then so should cooperative biju. --