Oh, I love a good Minerva fic and this is wonderful! And I'd never in a million years have imagined her with Kingsley, but I think you've found the right way to bring them together. I've always thought she might have a bit of a weakness for younger men and I can definitely see him being able to keep up with her and bring out that sense of humour we get the occasional peek at in the books.
Great job bringing in her relationship with Riddle when they were at school and how that would affect her ability to take on a leadership role in the war. Well done!