Tanya, sounds like a very ambitious series. I can see where you need to firm up future heroes and heroines to have them be in books before their own.
I usually start with what the H/H want and the worst possible partner for them to be with.
It seems a little strange (to me) for a person to think joining the military is a way to find love. I would believe more along the lines of someone he liked before joined, so he joins to follow her. Kind of like Starship Troopers.
Hope it all works out, because these sound awesome.
A Little Sweet. A Little Sexy. A Lot Happily Ever After.