Boss building (3.5)

[Dark_Nohn]

ATM, I'm building a 3.5 BBEG which I want the players to be done with by around level 10ish, it's currently a CR15, but as a single NPC following most PC rules. So far what I have for it is a half-black dragon doppelganger. It was originally going to be half-blue because of the blue dragon's ability to mimic voices (though it wouldn't be passed on in the half dragon template it would still be rather thematic) but instead went for black because of its aquatic subtype. It's also going to be recieving 5 levels of Warshaper, and 5 levels of Mindspy. Then the catch is, what do I give it for feats? What stat array do I give it? The players all have stats far above average due to exceptional luck at rolling, but as a general rule I don't roll stats for NPCs of any type