I was really excited by the most recent update about libraries, the spread of knowledge, and hints of deeper implementation in the future. I am sure that Toady has a ton of great ideas for this aspect of the game, but I just wanted to share my excitement about some of the potential possibilities I can think of down the road for this mechanic (and sorry if it has already been talked over in depth somewhere else):
- a realistically modeled spread of knowledge can of course lead to civilization variety, everything from uber-advanced civs with cutting edge weapons and armor, siege equipment, fortification and transportation systems to primitive wildmen civs with spears and clubs, which would give the game a lot of flavor
- obtaining knowledge in fortress mode to improve your fortress could become a really interesting sub-game of sorts, perhaps setting up inviting conditions for inventors and scholars, investing in research and development within the fortress, sending out adventurers and spies to gather knowledge elsewhere and bring it to you, interacting and trading with other civs for knowledge among other things...
- if knowledge spread is modeled somewhat realistically (such as in the Crusader Kings game), it should be randomized to a degree, with new technologies being discovered in a non-linear way, which always adds a lot of variety to each game
- in adventurer mode, there could be invincible villains/megabeasts that are immune to all weapons and attacks but have some weakness (think Sauron in the ancient battle, getting his ring finger sliced off or Achilles and his heel), and the adventurer would have to maybe go around the world, searching texts in libraries and other places to find the villain's weakness in order to defeat him, this would add an interesting wrinkle to typical "boss" battles.
- this might be my favorite possibility of all: I really hate how mages are implemented in pretty much all fantasy games. What they are is essentially a different flavor of a warrior: cast spell instead of swing sword and some minor differences, but overall, not what the lore image of a mage would have you imagine them as. I always think of a cooler, more lore-friendly version of a mage as a frail scholarly type who spends their time in libraries and magical labs, increasing their arcane knowledge, an arcane scientist if you will. Now, I have no idea obviously of how DF will implement them, but what I would love to see in conjunction with this library/knowledge system, is if you decide to become a mage as an adventurer, then the way to increase your magical power is to go around various libraries of the world (perhaps having to enroll in magical universities or secret magical societies/cults along the way to gain access to their libraries) and actually read the various tomes there in order to try to find clues about magical power.
This wouldn't be like coming to a library and seeing right away 4 tomes of architecture and then one shiny magical tome, but more like finding clues in regular books. Perhaps a historical poem that recites some ancient battle has a description of an ancient mage casting something, and the player could learn some part of the casting process from that, to be later combined with another clue from another book elsewhere. Maybe this won't be for everyone, but I feel like this system (or something similar to it) would be a breath of fresh air in mage gameplay and really differentiate mages from other types of adventurers/characters.