I had thought I could do more with women than making them "rewards" for the players to reflect their fame and charisma. But it's tough, because women don't have stats and they're hard to roleplay. Here are the different approaches I was trying.
I'm not sure what you mean by "women don't have stats." Everyone in the game world has stats, you just have to decide what they are. If your PCs are seducing first-level commoners, that's going to be very different from trying to seduce a tenth-level druid.
One guy is a sorcerer who likes to cast silent, stilled charm person on a different woman every night. If I ever want to have him accidentally charm a sea hag or something, I need to actually play out a couple of these incidents. But how can I describe the women other than hair color? My friend suggested doing it like this: "She's a six" -- where six is her Will save, or maybe her Will plus her charisma. That would add a defined level of challenge to the charming.
There are a lot of different ways to describe a woman other than her hair color. Don't just say "she's a blonde" or "she's a redhead." Go for some of the other features - how long is her hair? How tall is she? How old does she look? What color are her eyes? What color is her skin? How big are her breasts? What is she wearing? Does she have any distinguishing marks (e.g. a scar, a birthmark)? Does she have a wedding ring (or other indicator of marriage)?
You sound like you might benefit from having the
Book of Erotic Fantasy. It assigns a seventh ability score, called Appearance. This lets you easily make a numerical rating system for how attractive people are, so you can also fall back on this if you want.
I strongly recommend AGAINST using the rating system your friend has described. Firstly because it sounds like he wants you to describe how hard it is for the various women to be
charmed, and that's something his character should have absolutely no idea about until he tries it - don't forget to add their Wisdom bonus, not their Charisma bonus, to resist his
charm spell - and sees the results. A girl who looks like a vacuous airhead might shrug off
charms easily, while a frigid ice queen might succumb easily. The character should never know until he tries it.
Secondly, don't forget also that there are consequences to
charming women. First of all, if the
charm is saved against, the target knows that someone tried to use magic on them, though not who or for what (the spellcaster knows that they beat the save also). If it happens repeatedly, this could cause people to be on the alert as word spreads, and someone might connect the dots that it's your character. Moreover, a magical world would have laws taking into account the use of mind-altering magic. It's quite likely that your sorcerer, if he's found out, could be labeled as a sex offender, and persecuted as such.
Don't forget also that those under a
charm get to make an opposed Charisma check to avoid doing something they wouldn't want to do initially. A
charmed women who wouldn't be inclined to have sex with the character if it's not something she'd do when in her "right mind," and so is entitled to such a check. Hence, the character's
charm could still be wasted if he's using it for sex. Furthermore, there are no rules for what the victim of a
charm knows after the spell has worn off...it's quite possible that these women realize after the fact that they were
charmed, and so then report the character to the authorities.
Even without that, people don't live in isolation. Seducing women can result in jealous boyfriends, jealous husbands, jealous women that the sorcerer "pumped and dumped" previously (and now want him back...perhaps psychotically so), family and friends who worry (rightly) that the sorcerer is just using the poor girl for a good time, etc. That's not even taking into account what you mentioned, with monsters disguised as beautiful ladies. This character is just asking to run into a succubus who'll spend a night curled up with him, snacking on his levels.
Thirdly, sex itself has unintended consequences. Sexually-transmitted disease and unexpected pregnancies have been plaguing people who engage in casual sex since the beginning of time. Again, there are hard-and-fast rules for these in the BoEF, but if you want to you can hit your sorcerer with either, or both, of these consequences over time. Imagine having a son he never knew about who, brimming with anger over his father's never having been there, has grown up to be an evil character, and becomes the new villain.
Next I have my barbarian, who has been swimmin' in women. There's been a conflict established between him and his brother, the half-orc cleric. The cleric is the nicer guy -- higher wisdom, kind to the poor -- but the barbarian is hot on the surface and gets all the chicks. So I want the barbarian to get dumped a lot, while some lucky woman (like the dwarf ranger he just rescued) "falls for" the cleric over time. But it's tough to roleplay falling for someone, or even to keep the characters near the women that long when they're adventuring.
There's also no rule that says a character has to be attractive to all of the women all of the time. Imagine how the barbarian would feel if there was a town where the women valued kindness and piety, and didn't like shallow people...the barbarian would be all by his lonesome, while the cleric had girls hanging off of him.
And of course, the stuff about STDs, pregnancies, and social consequences can apply to a promiscuous barbarian just as much as they can a sorcerer.
Is it possible to have romantic relationships be an interesting part of the campaign? Or should I just tell my players, "Spend the money on ale and whores like everyone else."
I think it is. Just use them as a potential source of new plot twists and ideas, the same as you would every other part of the campaign, and they'll serve you well.
