Learning by Experience

As you've no doubt noticed, I've lately been pondering the way that Dungeons & Dragons handles experience. In particular, I've found myself somewhat dissatisfied by the way the game ties advancement in every field to advancement in level. I fully understand why D&D works this way and can respect the decision. For certain styles of RPG campaigns, I actually think it's a very good choice. For others, particularly those where cultural immersion is an important part of the fun, it's somewhat limiting (and, dare I say, unrealistic ?). 
Consequently, I find myself being drawn more and more to the approach to experience in Chaosium's Basic Role-Playing family of games. Now, BRP is quite unlike D&D in its design, being almost entirely skill-based, so there are limits to the lessons that can be drawn from it. Even so, there's a lot I like about its design, such as learning by experience, as presented in this section from the second edition of RuneQuest:
This version of learning by experience is, in my opinion, more complicated than it needs to be in its specifics. Call of Cthulhu – at least in its classical version; I can't speak to the current edition – makes use of a simpler version. Other BRP games employ their own variations. What matters to me is the basic conception of tracking individual advancement in each area of character's competency (skills), not any particular implementation of it. Indeed, I think it might well be possible to come up with a simpler application of it that nevertheless retains the core idea.
I don't know. My thinking is all over the place at the moment and I apologize if my recent spate of posts on experience and levels doesn't completely make sense. I suppose I am thinking aloud in order to decide what I like and want as I puzzle my way through the design of Secrets of sha-Arthan. Ultimately, my goal is a set of rules that is straightforward, if not not necessarily simple, and that is robust enough to handle a setting that's as culturally immersive as Glorantha, Jorune, or Tékumel (all of which are, to varying degrees, influences upon sha-Arthan). 
As always, I appreciate your comments.