Try doing this: If you lose the battle with them, you're forced to be with them and no one else. If you win the battle, you get the choice of continuing your quest without them or adding them to your harem.
Also for a sort of multiple ending, give the harem members optional scenes when you get to town and the more you be with her, the more she breaks you down until you willing make her your sole wife.
And for a "bad ending" make the more girls you arrive to Alice with...the less likely she'll accept you and more likely she'll just kill you instead.
0 girls: True Love ending
1-3 girls: Legal Wife ending (win battle with Alice) or Dominated Husband ending (lost battle with Alice)
4-6 girls: Harem ending (win) or Baby maker (lose)
7+ girls: Rejected ending (win and choose Alice) or Harem ending minus Alice (win and choose other girls) or Yandere ending (lost battle with Alice)
All available girls: Yandere ending (lost battle with Alice) or Big Harem ending (won battle with Alice and added to harem) or World's Most Wanted (win battle with Alice and choose her over other girls)
Something along this effect.
