The biggest problem with such a system is that everyone will, eventually, go for the 'template' setup - as in, choosing skills that will most benefit a character rather than go for individuality - so in the end, you will have, say, 90% of the entire WHM population choose specific set of skills while the other 10% will not, and because they don't, people will not take them/choose them to go to raids. Other MMOs solve this problem by allowing multiple characters, but because FFXIV can be played with one, such a system will cause imbalance between the population.