Before diving into my suggestion, I'd like to introduce myself. I used to work in the games industry (casual games and FPS) on the business side. Beyond being involved in the business strategy, for fun after work I contributed to beta testing for several games (e.g. Turok, Army of 2). I've since moved to a management consulting firm but I like to stay involved with the games industry; that's the reason I'm here!
I have a few simple suggestions to make the game more female friendly, and thus appeal to a larger audience.
1. In the unit creation screen, allow the creation of female units.
2. Provide visual character customization options (e.g. sovereign and soldiers can change hair colour, clothing colour, doesn't even require more character models, just textures).
3. Feature women prominently in roles throughout the game (e.g. soldiers, sovereigns), and in a normal way (i.e. normal looking women, not ones in bikini armor with giant chests).
4. Allow user to change the appearance of their soveriegn (e.g. hair) whenever they wish.
To men, these options seem superfluous. But to women, the ability to roleplay and "get into" the game is a critical component in the suspension of disbelief. Customization is one possible avenue to this, as is the ability to play as a female. It doesn't even need to be extensive; a few options go a long way.
Here's an example of this in another context. One game that I helped manage was a casual puzzle game called Paparazzi that was targetted toward a female demographic. The dev team initially put work into developing an interesting storyline, engaging puzzles, and beautifully drawn graphics. But of course, the dev team was mostly male. When we tested the game with a female audience our most consistent feedback was that they wanted to change their character's appearance. Once we spent a few days building customization options, the ratings from our female test group increased significantly.
The key learning was that men don't know what women want in games. We need to ask them.
Have a great day everyone!