The "No Sexual Intercourse."  As it sounds, not just you but also slaves without intercourse , masturbation or sexual occupations as well.  Also causes you to end up going without magic as well shortly into the game without a means to replenish mana.  There will also be some characters that you won't be able to utilize either.  It helps if you give everyone Miko outfits.  Otherwise you end up having people masturbate or go sex-crazy.

The "No slaves route."  You let your starting slave go, and not have any others except for the brief times they are required for the main plot line.  You are not allowed to capture anyone and must purchase those that the main plot line requires such as the human for the mage guild, the fairy (which will have to be the guild fairy, since at that point in the game you don't get the opportunity yet for buying it from anywhere else) for the mage guild, the taurus for the mage guild, the elves for the lady by the cliffs and so forth.  Those who are required for the main plot line you are not allowed to have work or quest with you while you have them (Library is ok for training but nothing else).

"Good Guy" Challenge: You have to be a "good guy" who does everything "by the book".  You are not allowed to kill prisoners, cannot kidnap innocents (or kill them) and cannot rape anyone, whether they belong to you or not. Elven patrols are considered innocents and cannot be attacked. You are free to purchase slaves and capture bandits as well as ask people to join you, but NO branding. Jailing is acceptable but farm is forbidden. No Umbra occupations, and no sex work unless the slave has fickle, deviant, or pervert.

The taurus girl main quest also requires additional steps. (Because Melissa implies these requirements and I'm 95% sure it used to be a requirement.) In addition to a taurus female with giant, lactating breasts, she also has to have the lab modification of multiple breasts. (Maximize nipples, develop rudimentary nipples.) Cannot use these potions: amnesia, aphrodisiac.

Must pick the good ending and also choose to save your slave.

For an optional addition, you have to fulfill the repeatable quests as closely as possible and cannot fulfill the darker quests like brothel work and untamed rich slave.

By the books is more of a role-playing challenge, which I dig. With sex workers being the highest earners in the game, it would be a bigger challenge to earn money too. Think if I tried it, I'd extend the rules to intimate interactions, you must never take an action there that causes a slave stress (save beforehand). That way your mana earnings are hindered by not being able to have multiple partners without them both being fickle, or pair certain slaves unless they are bisexual/homosexual. Making those traits MUCH more valuable, so far they've been a bit meh because you could just give it to a slave easily.

Came up with another challenge thinking about this.

Second Fiddle: You are master in name only, the real power behind the mansion is your starter 'slave', who you must do everything in your power to please. Take time to consider their personality, remove the grateful trait, then edit on any traits that are appropriate. Are they Dominant, a Coward, Fickle, Clingy, Scarred and/or Spoiled?
Quickly get them to the point where they can take charge in the bedroom, then almost always have them present and in control when performing intimate interactions. Like you, they should never have to work, leave that to the actual slaves. And always imagine what they want when determining what to do next, do they want a certain race of slave to play with or a bodyguard with specific traits? Did they fall out with someone and want them punished? Do YOU need to be punished for failing to complete a set task or for not meeting their luxury requirements?

(EDIT: starter slaves now have their own missions, so maybe don't bother with save editing. At least hold off until those personal missions are completed, as they give the starter some traits depending on your choices)

• NO BUY : not buying any slaves (either from guilds, sebastian or slavers).

You can recruit story characters , but for all others you have to capture them in combat. You can allow recruitement of liberated prisoners if you want, but only after defeating the bandits or slavers that captured them. For harder version, no story characters allowed, capture only.

• NO SELL : you can't sell any slave to anyone (except for main story quests when required). Means you can't use that as your source of income at all (no slave guild contracts either).

A one city works challenge worls surprisingly well! You are exiled to your home city (Gorn or Frostford) and the other cities will not trade with you. This means you cannot enter the other slaver's guilds, buy from the other merchants, buy spells from the mage guild, buy portal stones, send your slaves to work outside your city, etc. You can still talk to people in those cities for quests and take public transport home. You can trade at Shaliq village. If you get blocked by a cheap shop bought item that will require high level random chest loots to solve (basic liquid for Melissa's youthing potion, a slave wanting lacy underwear) then you can buy an item for that use only. I'd also suggest playing this Iron Man with no rollover of the slave contracts by extra reloads (as that is an exploit for infinite money, essentially).

This scenario works well as mansion points are important and you need to make better decisions. You get to use all the tools in game that you usually bypass with easy magic. Some parts of the game even look better balanced than in the full game.