Mdd, those are your opinions. In any case, even if he was an Acharon later Acharonim can pasken like him if they think that he is correct. I already brought that Acharonim sometimes disagree with Rishonim so you apparently disagree with those poskim as well as those poskim who hold that appointing a king is a mitzva kiumit. I disagree with you and apparently you have no answer as you have resorted to an ad homiem argument.
Zahavasdad, many peoples in their empire had local kings. The Herodians were called kings even though they were subject to the Romans.