It occurs to me that any of the old gods would be INFURIATED by what Voldemort has done. Raising the dead, and proclaiming himself a god is exactly the kind of thing that can get one in trouble. The Roman gods, especially, were ruthless in striking down those who displayed hubris. Hera is usually portrayed as a nagging shrew, continually throwing tantrums at her cheating husband's one-night-stands, but she was a major power in her own right. Persephone might be able to get her husband involved, if he isn't too angry at her capture.
If Harry swears to release his captives (slaves) upon Riddle's defeat, it might significantly reduce ill-feeling. is Harry intending to demand that his Ladies only have sex with him? I really hope not - he'll never have time to win the war.
Author's response
Harry won't demand for them to have sex with him at all, since he's not in this to really get laid, he's in it to gain their loyalty, and in effect, their powers. Sex is the only way to induce their highest magical probabilities though. (But that doesn't mean he won't get some every now and then ^_^ )
And while Persephone's husband might kick VOldie's ass around, Hades is no longer in existence. I'll explain why most of the other entities such as Lilith don't explain anymore, and why exactly there are no such things as 'gods' or 'goddesses' to the Wizarding World in the next chapter.