Instead of one concept for ALL your gals, consider having each gal stick with one concept for life. So when you start running into missions your current gals can't handle, come up with a new concept and hire new gals to follow the new concept. As gals get killed off, you can decide if you want to hire replacements for the older concepts or to let them die out. This way you will have a chance to win the game and still be able to explore your concept ideas. It is up to you to decide if mission deployments can consist of more than one concept, however base defenses will likely be made up of gals from multiple concepts.