I've revisited my outer space ideas and came up with this new one:

It's far in the distant future. With humanity finally establishing inhabitable colonies in space they move to solve the overpopulation problem. Unforunately, one of drastic steps they take is denying most of those who left the opportunity to visit back.

About three generations have passed. Earth finds themselves now suffering for their extreme population plan. Women make up about 35% of the population on Earth. Most of them are middle-aged and above. So a new campaign is launched to promote young women from the other worlds to migrate back to the homeworld.

On one colony the people will eventually find themselves at odds with Earth's campaign. One group is a squadron of all-female soldiers. They are stationed near a town that an Earth ship is visiting. In that town is an all-girls school that was formerly a religious school. It's earned the reputation of educating the brightest students and leading athletes.

One student, along with the female soldiers, will later discover that Earth doesn't really want any women to migrate back to Earth. Their cultures have changed too much from Earth's. Instead, they realize Earth's ambassadors and doctors just want their DNA to clone their own women.