Mixed harems are one way to do it. Max Gentlemen's Sexy Business is the perfect example. Six Seven Eight characters of each gender with the same unlocks for every one of them.
https://f95zone.to/threads/max-gentlemen-sexy-business-v2-18-the-men-who-wear-many-hats.46787/
A few honourable mentions:
https://f95zone.to/threads/translation-request-bible-quest-develop-by-frog-flying.95327/
https://f95zone.to/threads/magic-castle-repurearia-v1-23-house-of-black-dream-fantasies.102706/
https://f95zone.to/threads/max-gentlemen-sexy-business-v2-18-the-men-who-wear-many-hats.46787/
A few honourable mentions:
https://f95zone.to/threads/translation-request-bible-quest-develop-by-frog-flying.95327/
https://f95zone.to/threads/magic-castle-repurearia-v1-23-house-of-black-dream-fantasies.102706/