I think developing a general system of combat that would work fairly well with all types of systems, would be a good endeavor for someone. If Mongoose did this, I think it would help to "universalize" all types of games.
The main reason CCR uses the Aiming Point, is that CCR does not use Armor Class. It deals damage directly and armor subtracts directly from the damage done. Also, using William Carlson's expanded rules gives each Aiming Point a Color Result you need to match, in order to hit that location. If you do not get the proper result, but still hit your opponent, then you can roll for a random location or role play out where it might be. It is difficult for those that have only played using D20, to understand the exciting options CCR offers as a RPG system. You could use a D20 with this system, and even add a "general" Armor Class. You can add Saving Rolls or just about anything from the D20 system, and CCR will just absorb it. You may think that this is not possible, but it can be done.
I would like to say that D20 is a fine system, but a set group of characteristics, abilities exclusive to classes (just make the abilities more difficult or expensive for other classes), and any number of limitations to the system, makes it far too hard to play sometimes. You end up tossing out a lot of things, just to save time. Before long, it becomes a wargamers RPG.
But the background material that Mongoose and other Conan games and modules provide is excellent, and CCR is limited in this. But that's not a problem. I can use any material for CCR.