How would you represent evolving relationships in solo play?

As the title says, "How would you represent evolving relationships between characters? "

If you don't necessarily want to do it by fiat, or by asking Mythic questions all the time, could we take a page from "The Sims" computer game? If I remember correctly, each Sim had a number of preferences. I don't remember exactly what they were, but let's assume that a Sim character might like or dislike things like soap operas, creative writing magazines, gardening, horror movies, country music, and mountain hiking.

For example: 

Rebbecca  likes: creative writing magazines, soap operas, and mountain hiking
Rebbecca dislikes: horror movies

Robert likes: horror movies, gardening, and soap operas
Robert dislikes: mountain hiking

When I've played that game, and let the Sims "converse" with each other, I could see little dialogue clouds with ideograms. If one was talking about travel, you'd see a drawing of an airplane, for example.  Then if the other Sim liked it,their relationship score got a boost (a "+" would float above their heads). The higher the relationship score, the more options become available to you as a player to make them interact (i.e. if the relationship score got high enough, you could then hug the other Sim, etc).
On the other hand, if one Sim happens to bring up a subject that the other Sim doesn't like, then the relationship gets a "-" (minus) and the score goes down.  If the score goes down below a threshold, you might lose some of the options in a relationship. I don't remember what happens if the subject is was neutral, so I'll have to play again sometime. :)

Anyway, I think this is another idea that could be tweaked and integrated into solo play to add more guidance to NPC reactions.  I'm still hazy (as usual) on how exactly to tweak it, but here's what I'm thinking so far:

• Relationship scores is easy to visualize.
• Likes and Dislikes (or whatever) are probably a little harder. They should probably be both broad and evocative. "Gore Hound Geek" is probably more evocative and covers more ground than "likes Horror movies".  I really like what I read on this post regarding Sorcerer's Descriptors (http://indie-rpgs.com/archive/index.php?topic=11194.0), which is what inspired this bullet point.  Maybe Personality Traits is a better word than Likes/Dislikes. Thoughts? (Note: I think The Window rpg might be very much like this as well).
• The player could randomly set an NPC's Descriptors/Personality Trait via UNE or Mythic (or Tarot cards in some creative fasion).
• I'd probably roll for Personality Traits only at the last possible moment (i.e. when I try to interact in a meaningful way with the PC.) I have more thoughs on this and may need to unpack further.
• If the Personality Traits becamo relevant in a scene for whatever reason then I could use them as a guide of whether the relationship gets a "+" boost or a "-" reduction.
• I would, in turn, use the relationship score as a guide of an NPC's disposition towards me.
• Common sense, the needs of the fiction, and what has been established about a character should prevail, though. Not everything that could affect a relationship score can be covered in descriptors.
• I'd personally make it a requirement that in order to use someone's Personality Trait to your advantage without a roll, your own declared Personality Traits must be conducive to that. If you don't have it written down, if your mental character concept of your PC allows it, then you can use it as well ( see "common sense" bullet preceding this one).

For me, the whole point of trying something like this would be to minimize fiat as much as possible, and minimize the need for Mythic questions.

How would you tweak this approach? What other approaches would you use to roleplay PC/NPC relationships?