When I think about it, probably with too much naive 'realisticness' as the ideal, I'm dissatisfied with the increase of hit dice at each level up.
Think of a technically proficient guitar player--isn't he about as good as he'll ever be once he masters the instrument, say as a teenager like Clapton and Page? They might get wiser but are they going to play with all that much more technical proficiency?
So, if a guitar player is like our fighting man, isn't he 95% as good as he'll ever be when he sets out for glory as a strapping youth? Wouldn't it be even more glorious if he ended his career showering in golden coins upon a raft of his enemies' long bones, floating on the river of the blood of all the world's dragons, if he got to that point without all those extra hit points--if it was the treasures and storied arms he gathered in his adventures that made him great, not a game mechanic designed to make it easier for him to achieve greatness.
Wouldn't this make gold equal experience in an even more fundamental way?
Something new would have to devised to handle access to higher spell levels, and a skill system (which I guess is the way this concept is usually handled) would seem to be very appropriate in this form of the game.
This idea appeals to me. I'm interested in the opinions of the wise on this matter--though apparently not enough to pose this question in a forum where any of them will see it.