Background
  • Currently, the skill training treatises are purchased from the crafting guilds with guildmarks.
  • Currently, some recipes list "recommended training".
  • Not having this recommended training apparently increases synthesis failure rate, increases likelihood of instability, and causes worse failures (e.g. 3% progress and 20 dura loss on standard fail instead of 10% progress and 10 dura loss).
  • In patch 1.19, treatise requirements are being removed from recipes.

Suggestion
Re-purpose the skill training system into a form of crafter specialization.

The key concepts are listed below:
  • Treatises are only utilized at a higher rank range (perhaps rank 40+).
  • Treatises would be required in order to attempt certain types of recipes, or to achieve certain types of results.
  • Treatises can be purchased using guild marks from the crafting guilds, purchased from the Grand Companies using seals, or available as quest rewards.
  • Treatises may require other treatises as a requirement.
  • Most treatises can be acquired with 6 to 10 hours of gameplay, spread over a couple of days.
  • Hundreds of treatises will be available.

To keep each post readably short, I'll post further details of each point following.