the next minecraft update is going to add a lot of interesting stuff, including the ability to unlock recipes (custom recipes are planned for 1.13) and advancements which are an improved achievements system. and if i'm not mistaken custom advancements can even be added by the server without client modding. this would allow for some fantastic skill trees and stuff, and in cooperation with the recipe unlocking this could a great and simple system to allow players with certain skill levels to unlock certain recipes.
there will be a new gamerule called doLimitedCrafting that is false by default, meaning everyone can craft anything, when set to true players need to have unlocked a recipe (via commands/wisdombook - it's more for mapmakers than survival) to craft it. i think that implementing crafting restrictions in this plugin that overwrite the gamerules set on the server would make little sense. so i think it would be best to add crafting skills, but only limit the ability to use not yet unlocked recipes when the gamerule is set to true. that way admins don't have to completely miss out on the skills if they don't want to limit their players crafting.
some skills i'd suggest: (each of those should be discussed in more detail in seperate github issues)
a generic crafting skill
a repairing skill (though i dislike the idea of using iron/gold blocks, especially now that anvils are in the game for a while already, something better should be figured out)
a salvage skill
engineering skill (similar to the one suggested before, i think if used with the new systems it would make a lot more sense. as in it would add a challenge when you want to build machinery and have to look for players with a high engineering skill to make it for you; could be used for crafting mechanical items, redstone related, etc)
smelting skill (requires a furnance instead of a crafting table, but it's the same concept i guess)
smithing skill (for crafting metal tools, should metal tools that have been crafted need to go through an extra crafting step involving a furnance and/or an anvil for more realism?; higher smithing skill level could output more durable weapons/tools)
leatherworking
fletching (arrows)
tailoring (banners?)
jewelcrafting (raw coal, diamonds, emeralds, etc stay in their ore form when mined - to refine them you to use the jewelcrafting skill)
a cooking skill (has recipes for crafting and for furnances)
etc?
the suggested alchemy skill could make use of this system too.
i'm aware that those skills are different from those "active" skills this plugin mostly has, in that you have to sit down and work on what you're doing instead of running around. and therefore they obviously limit the possibilities for skill abilities, but i think that even without abilities crafting skills would be a great addition to the plugin because they would add a completely different challenge to the game while still being playable in survival without admin intervention (which the 1.12 system wouldn't be since it's mostly for mapmakers). and i think the possibility of creating better weapons/tools (smithing), getting more and possibly nicer gems out of your ores (jewelcrafting), cook more filling dishes, and other gradually improving passive abilities would be a good substitute to active abilities.
the next minecraft update is going to add a lot of interesting stuff, including the ability to unlock recipes (custom recipes are planned for 1.13) and advancements which are an improved achievements system. and if i'm not mistaken custom advancements can even be added by the server without client modding. this would allow for some fantastic skill trees and stuff, and in cooperation with the recipe unlocking this could a great and simple system to allow players with certain skill levels to unlock certain recipes.
there will be a new gamerule called doLimitedCrafting that is false by default, meaning everyone can craft anything, when set to true players need to have unlocked a recipe (via commands/wisdombook - it's more for mapmakers than survival) to craft it. i think that implementing crafting restrictions in this plugin that overwrite the gamerules set on the server would make little sense. so i think it would be best to add crafting skills, but only limit the ability to use not yet unlocked recipes when the gamerule is set to true. that way admins don't have to completely miss out on the skills if they don't want to limit their players crafting.
some skills i'd suggest: (each of those should be discussed in more detail in seperate github issues) a generic crafting skill a repairing skill (though i dislike the idea of using iron/gold blocks, especially now that anvils are in the game for a while already, something better should be figured out) a salvage skill engineering skill (similar to the one suggested before, i think if used with the new systems it would make a lot more sense. as in it would add a challenge when you want to build machinery and have to look for players with a high engineering skill to make it for you; could be used for crafting mechanical items, redstone related, etc) smelting skill (requires a furnance instead of a crafting table, but it's the same concept i guess) smithing skill (for crafting metal tools, should metal tools that have been crafted need to go through an extra crafting step involving a furnance and/or an anvil for more realism?; higher smithing skill level could output more durable weapons/tools) leatherworking fletching (arrows) tailoring (banners?) jewelcrafting (raw coal, diamonds, emeralds, etc stay in their ore form when mined - to refine them you to use the jewelcrafting skill) a cooking skill (has recipes for crafting and for furnances) etc? the suggested alchemy skill could make use of this system too.
i'm aware that those skills are different from those "active" skills this plugin mostly has, in that you have to sit down and work on what you're doing instead of running around. and therefore they obviously limit the possibilities for skill abilities, but i think that even without abilities crafting skills would be a great addition to the plugin because they would add a completely different challenge to the game while still being playable in survival without admin intervention (which the 1.12 system wouldn't be since it's mostly for mapmakers). and i think the possibility of creating better weapons/tools (smithing), getting more and possibly nicer gems out of your ores (jewelcrafting), cook more filling dishes, and other gradually improving passive abilities would be a good substitute to active abilities.