Tavis,
I think you are making some assumptions that aren't necessarily true. Consider a different perspective on advancement as-is before scrapping it for something else:
Firstly, why wouldn't your character know how much Hx he has with other characters? The Hx rating is an abstract statement about how well your character knows somebody else, and thus can assist them, or interfere with them. Your character is the one who knows the other person, he should know how well he knows them. It's not absolute, of course, but that's where the die roll comes in.
Secondly, why wouldn't your character know which stats are highlighted?
Let me unpack that one. I'll use D&D as an example because I know that you know.
You say you want player motivations and character motivations to align. Cool. But advancement and achieving your goals aren't necessarily the same thing. They are in OD&D: you become a better adventurer as you find more treasure. Does this really make sense in the fiction? If I get luckily and find an unguarded chest of gold, why should I get better at fighting monsters?
(Note: You can sub in anything else for getting treasure: getting vengeance on enemies, building a better society, getting the girl, finding a safe way home, etc. The only time your character's goal is exactly the same as advancement in a game is when your goal is to advance the way the game allows you to advance.)
When a stat is highlighted, that means your character will grow and benefit from that experience. It has nothing to do with success at other goals. If your Charisma is highlighted, you will gain experience from holding parleys, regardless of whatever other benefits you might get. The game won't break if your character knows this.
So, if you are raiding dungeons, your main goal is to get rich, or at least recover wonders from the old world. So yeah, you could take the easy route, use all your wits to bypass traps and monsters, seize the treasure and get out. Your reward for that is treasure, as it should be. But unlike D&D, if you want to become a better adventurer in Apocalypse World, you have to take risks.
Is it strange that you would mark experience for certain stats but not others? Maybe. Or maybe these are the things your character thinks he should be doing in order to become more knowledgeable and skilled. If his sharp is marked, he is thinking that he needs to keep an eye out more, watch people more closely, so he can get more info on what's up. He's not thinking about how he should beat people up to get better because his hard isn't highlighted.
You character can still parley only when it makes sense to achieve other goals, like bypassing monsters or trading information, but what about holding a parley when he thinks it will help him becomes a better bargainer, or when he thinks it will help him understand and deal with people better in general?
Anyway, that's another way of looking at it. You really can swap it out for a system that characters are aware of, without swapping it out.