This is an absolutely amazing idea. The God of War cross is great, I really like the idea of a Kratos version of Harry. It looks like he will be entirely unforgiving when it comes to protecting what he sees as his.
As for Hermione I like the idea of the Valkyrie of your three but I agree with Cateagle with the idea of one of the furies, it fits really well with the God of War idea. I look forward to seeing what happens with this.
Cel