I like the idea of having it be as flexible as possible. For my players and me, the charm of RM since 1981 has always been that your character is as individual as a fingerprint, and the old "Why can't I __________?" that D&D GMs had to put up with from their players magically disappeared. If you learned how, you can. Even if you didn't learn how, you are welcome to *try*, although I may not think much of your chances.
I figure the reason HARP hasn't replaced RM in its entirety is because there are still too many "anti-heroic" gamers out there who want their gritty realism. Well, the most fundamental part of realism is that no two people are alike, and that you become the person you *choose* to be. In a practical sense, there are as many "character classes" as there are players. To that end, I'd like to see a character generation/management system that allows you to choose how many areas of focus you have and where they are, and adjusts skill costs accordingly. That way the guy who always wants to create a character the system simply doesn't allow for (there's always one) is stymied. Once again, "Why can't I __________?" has an answer: You can, but you'll have to put up with balancing weaknesses just like everyone else.
Personally I'm thinking along the lines of a computer application of some sort. You highlight the areas you wish to be your strengths, and the program adjusts your skill costs accordingly and displays them in another window. The more areas you highlight, the more the entire skill set moves toward average costs. The fewer areas you highlight, the more things in your strong area are cheap and those outside it are expensive. When you are satisfied with your skill set, you go with that. What you call that character is up to you, but if you find yourself being burned at the stake by the local peasantry because you claimed your character profession was "Mega Uber God", don't whine to the GM about it. It's not his job to prevent you from learning from your stupidity.
Note that the hard part about this idea is judging "skill similarity". If you choose to have melee combat with bladed weapons as a strong point, how does that affect skinning and butchering an animal? Likewise, does the ability to throw fireballs affect your ability to get a campfire going *without* throwing one?
The bottom line is that it has to be kept real to keep us gritty realism junkies happy, but at the same time it has to be kept as simple as possible so keeping a decent pace to your game doesn't become an exercise in frustration. That's why where possible I'd like to have applications to keep the number crunching drudgery in the background.