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)