Achilles as the gay sidekick and Hippolytos as the straight one... I like it! Diana could use a blood-relation in the form of a brother / cousin, that would really be great.
The concept of a "Wonder Boy" or "Wonder Lad" strays a bit from the mythology aspect of the character, which could be a good thing. I definitely think that Diana needs a gay male younger hero to serve as the mentor for. if Achilles was presented as a younger, headstrong warrior who needed Diana to educate him in the ways of the modern world... i'd be happy.