Hello
Currently, it is painfully slow to level up soldiers in their melee skills, unless one uses the Danger Room. In my opinion, Skill books should be added. Books would allow the transfer of information and skill much better than idly standing around, doing absolutely nothing, however, books would be painfully expensive, slow to create and also one must be able to read the book to use it.
For example, a Novice Axedwarf would be able to pick up and read the "Manual of Arms: Axes" and learn quite a bit from it. After a month of study, he would become a Competent Axedwarf.
Some Dwarfs are unable to read, so an option to teach them should be available. One could set up a class room where the assigned dwarfs would learn skills that their teacher has, allowing children to be Proficient smiths, farmers, clothesmakers, etc... and not just bait for the snatchers/experimentation subjects
The teaching process could again be sped up with books. If the teacher has a book, the class learns 20% faster about a topic. If half of the dwarfs have the same book, the class learns 40% faster, and when all the dwarfs have it, the bonus becomes 50-60%
Quality should also become a factor. There is the quality for the object, but also quality of the writing within. The quality of the item increases its value, while the quality of the writing increases its value and teaching ability.
Presses should be made to copy books quickly, alternatively, the book keeper, or a scribe can copy the books by hand.
Dwarfs that can read and write would be able to write books of their own that could be copied, distributed, sold.