I just posted an idea the other day for a stats mod to try to make leveling work like you guys are talking about.
I am considering making it, so I'm glad I came across this discussion
My ideas are in line with what VeryEvilDudeofDarkness and Lord Umbrage are saying.
I don't agree with the flexible capping. You should not be able to train everything at once and maintain proficiency, even before level 100.
You have to compromise. Do you want to be great at a few things or do you want to be good at most things?
My thoughts were that all attribute and skill levels should fluctuate based on how much they are used, your race and your profession.
I've had this idea since I played TES3 the first time and really liked the natural skill development but it still lacked an immersive quality.
Every attribute and skill should be like a muscle. The more you use it, the more it grows, the less you use it, the more it shrinks.
Think about how the power meters in some old school games used to work.
You press the button as fast as you can and the power bar fills up but if you slow down, the powerbar starts to trickle back until it reaches the point where you are maintaining the power level.
How fast a stat deteriorates should depend on how much effort you have already put in to learning it.
The more you forget, the faster you forget.
This would also effect how easy it is to learn a new skill since the more experience you have, the less you forget.
Starting out would be a hump to overcome, just like in real life. The initial handicap would make race and profession much more important at the start.
To compensate the speed of regaining a skill after it has been neglected, you adjust the level rate by how much experience has been forgotten compared to how much you remember.
So if you have trained a long time and forgot a little bit, then you can regain that very quickly.
But if you forgot more than you remember, then regaining that experience will be much more like the first time training.