Maybe have a morality system for different playthroughs for eample.
Good - Your "Harem" love you and will fight for you in your army they not only wish to see your goals accomplished they also share your vision they love you unconditionally and sex is loving and kind Bonus: You can maybe take certain lands via diplomacy with the help of your treasured girls Bonus 2: You all cuddle in the same bed?
Bad - Your "Harem" isn't made out of love they are spoils of war nothing more nothing less they are breeding stock whose sole purpose is to birth you mighty soldiers to fill your ranks and help take the lands by conquest you don't care about love you care about sitting on the thrones of these lands and the advancement of your legacy ( Bad route has more fetishes such as BDSM and pregnancy all that also Girls will NOT help you nor FIGHT for or with you )
Maybe add a "Settlement" system to go along with this? Start out in a hut and eventually be able to build a small village? Just a idea.