I really like something Mike Mearls posted in his Legends and Lore series, and was refined by Monte Cook. It addressed something that has long troubled me about D&D in particular - an issue of what I call escalation. Since the current skill (and most other) systems has character's skill escalate with level, even a fighter in platemail would eventually be able to swim (even in full plate) - unless the DC for doing that scaled upwards as well. To me that is a pretty flagrant breach of realism. Shouldn't the difficulty of doing that remain constant (and in fact, Impossible)? I want to extend those ideas into a complete skill system that could run in parallel with the rest of 4e in your game right now.
The proposed system turns the skill system around. Instead of skills having tasks that they enable, tasks require an ability to overcome. For example, climbing would (always) be a strength check. A character can also be trained (in a specific ability based skill) - which would add a bonus to that activity - so for example, a trained climber can add 5 to their effective strength (or any other relevant ability) for climbing purposes. Examples of other abilities used in climbing would be: hanging on to a ledge for a minute:- Con. Swinging cleanly through a window on a rope:- Dex.
Raw ability should not let you do Expert tasks. Mike goes on to suggest that training be in (named) levels. Then essentially, the ability would be the measure of how good he is within that capability band. And perhaps the character gets to add the training bonus to the raw stat when rolling.
Trained level DM to relevant ability check Activity you can accomplish with DC 10
0 - untrained -3 You have no training at all.
1 - Novice 0 Novice tasks
2 - Journeyman +3 Journeyman tasks
3 - Expert +6 Expert tasks
4 - Master +9 Master tasks
I deliberately make untrained characters suffer a negative - this is for niche protection. Character classes would give Novice training in every class skill. Then the character can add a few more points to skills as desired.
Task level (relative to your expertise) DC
One below (eg: you are Journeyman, task requires Novice) 5
Equal 10
One above (eg: you are Expert, task requires Master) 15
Two above 20
Three above 25
Four or more above Impossible
So, if the DM tells you the task requires a Journeyman, and you are trained to Journeyman level, and your ability + modifiers = 11, then a simple check with a DC of 10 will accomplish the task - you could do it by taking 10. If the task was a Novice task, you would get +5 to accomplish it (meaning an effective DC of 5), if it normally require an Expert - then an effective DC of 15 would be required.
Note that you can always accomplish a task within your capability (by taking a 10, essentially). Novice tasks likewise would not normally require a roll (and will be even easier to accomplish if a roll is required).
As before, some tasks would require training to perform - and so no amount of ability would let you perform them untrained. As described above, training adds 5 to your ability to accomplish the specified task.
What I like about the above system is that training will trump raw ability, but raw ability remains important (and will decide between tow characters of the same training level). A trained Expert with a Dex of 10 will be able to do tasks that require no training as better than someone untrained with a Dex of 18. The same kid with 18 Dex will not be able to perform tasks that require training at all, never be able to perform Master tasks, and will need a 15 or more to do an Expert task (one that can be performed untrained).