You could actually have your girls learn specific spells that they can use against customer's (and yourself if your not careful) to either protect themselves or maybe even improve their job performance by a small percentage whether it's in the brothel, stripping, or for the movie.
Can almost do that now. We could create specific spells as items and have them reduce mana and boost %chance to do <whatever>. We'd really want a new equipment slot for memorised spells, but apart from that, it's doable by making new items.
Of course, to be really worthwhile, you need to be able to report the effect. I mean, imagine a stripping enhancement spell. This is something the girls casts as part of her dance. The dance is the spell, in point of fact, and when she dances it, it creates an illusion that works its way into the minds of the patrons and brings them right up close, close enough the feel the heat radiating from her skin, and the warmth of her breath against their cheek. All the other patrons fade away; for each person watching, they get a private dance meant especially for them, and the enchantment of the moment is such that they can feel the dancer's building excitement, share her growing arousal as her moment approaches, until ...
... until the music ends and she walks offstage leaving the patrons panting for more. Litterally.
That's the thing, really. A silent +5% to stripping skill doesn't really add that much to the game. But give it a decent bit of game narrative, and it becomes worth changing the game to allow user items or events to override standard event text. The player needs to notice something happening.
Have an item and/or spell to transform him in to one of your girls.
I must admit, the whole TG thing never did much for me. But you could do the basics with existing scripts. Have a menu option that deleted the customer and created a new random girl in his place. You'd need to change the sell customer button and link a script to it, but that should be doable soon enough.
If you really want to get complicated (like this isn't already there) it could carry a risk. The wizard may not be above taking a few bribes so you may need to offer some "incentive" (money, girl, quest, etc...) from time to time to stay on his good side.
The whole issue of PC risk needs some attention. I mean some of the girls in the game are probably capable of single handedly taking on armies, and winning. How the PC holds them has always slightly concerned me...