A more plausible option for achievements would be putting in trials or feats that you have to accomplish to become recognized in a particular skill or to gain the next rank in a particular skill. IE to move from apprentice to journeyman in destruction you have to pass a trial of destruction that could be achieved independently or through a guild. The PC achieving through the guild may be given certain advantages as a benefit of being a guild member like guidance, maybe a free spell to assist, a convenient guild operated trial where as a PC achieving on his own would have to do all of these things on their own.
I like the idea and have posted something like that in http://www.gamesas.com/index.php?/topic/1144150-character-development-and-you thread.
Edie: I copied the part about this subject:
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Character Skills.
Skills and their developments are one of the more important aspects of the character development in the current RPG games, so it has to be implemented in a way that would satisfy the average gamers, without confusing them.
The players have to sense their progression without having to look at the numbers, and those skills have to be chosen and developed for characters because they are needed for the character, or give the players more satisfaction to have them, and not because of some problematic system that forces the players to choose them for their characters.
For instance in Oblivion you chose a character class with primary skills that you do *not* want to use to avoid gaining level, because gaining level actually makes the game harder for the players.
But if gaining levels was a sought event like in Fallout series, and enough advancement in any of the skills would result in a level gain, and character class and its primary skills would help shape the final character in a more definite way, then it would result in a more straightforward game-play and more enjoyable game altogether.
I have a lot to say about skills and the best method of their implementation in an RPG game, but it would need a separate thread of its own, so I stop here and do not even make a poll about them, because some of the poll choice items would need detailed info which I want to avoid here.
I just want to talk about their progression rate and their limits now:
IMHO you should always be able to raise your skill levels as you practice them without any hard limits over their cap, but there should be a soft cap over your skill advancement.
So you start a skill at level 5 for instance and you are called "Novice" in that skill, you can advance your skill by practice, but in order to be called "Apprentice" in that skill, you have to find at least a journeyman teacher of that skill and prove to him that you are a worthy apprentice for him so that he would accept you as his apprentice, and teach you the initial tricks of apprenticeship on the skill.
So when you are a novice in a skill, you would have a soft cap of 25 over your skill advancement, so until that cap level, you can freely improve your skills as you like, but of course the progression of that skill will slow down a bit as you raise your skill level, but as you reach the level that is the current soft cap over that skill, your skill progression rate starts to drop significantly more as you start to advance in that skill, so for the next few levels, the progression rate is still manageable, but soon you would find out that you need to attend to that skill master and become his apprentice in order to be able to improve that skill in any acceptable rate.
After you are officially acknowledged as an "Apprentice" in a skill, the soft level cap over your skill progression raises to "Journeyman" level which is probably 50, and your skill progression rate reverts to the normal uncapped level, but as before it starts to drop a bit as you raise your skill level, and after the new cap you have to seek a higher level master, or current master if he can manage that (at least an expert in that skill), to become a "Journeyman" in the skill, and raise the cap to the "Expert" level, and so on...
So an "Apprentice" level teacher can teach your novice level character about a skill, but you need to find a "Journeyman" level teacher to be able to get acknowledged as an "Apprentice", and also those masters might ask for a fee for this task and might even send you for a quest of their own before they graduate you to the next level of mastery in that skill.
When you are at "Expert" level of a skill, in order to be called a "Master" of that skill, you have to find the unique grand master of that skill, and become graduated as a master of that skill, that would be at level 100 or a few level above that, and after that you would not have a solid cap over your skill progression, but the rate of your skill progression would start to drop as you advance your skill until the time that it would practically take weeks before you can raise your skill level from 145 to 146 and so on...
In each advancement in the skill mastery, the road for you to gain some new skill perks would open, so some perks require you to be actually acknowledged as an "Apprentice" of a skill, and some perks need you to be an "Expert" in that skill, but unlike Oblivion, I suggest that those perks need to be learned from their appropriate teachers not automatically gained as you reach the required skill level.
I will write more about perks in their own section.
I think that each graduation to a higher skill mastery level requires a minimal level for the attribute governing that skill, so if you need to become a journeyman of Marksmanship, you need to have at least 40 agility, and to become an expert one in that skill you need at least 60 agility and so on...
If we play a game that does not let us raise our attribute much in the course of the game than those requirements should be a bit lower.