I have a mod idea that ive been looking around for.
Basically its an RPG leveling mod. Where its fully customizable though the configs where a player can say.
You get this much xp for punching wood in woodcutting
and you need level 5 woodcutting to use a stone axe. I would want it customizable so that modpack makers/server makers can make their own custom and unique level trees with whatever mods they have.
What would be even better is if you could in the config choose/name what the skill is so a modpack/server could have many or as few skills as they want and they would just have to define using this item on this block gives you xp in this skill.
The other idea that would fit well with this or could be its own separate mod is a mob leveling system where mobs get their own levels and the farther you go from spawn the higher and stronger they get. and you could customize their loot and drop chances with how high of a level the mob is at. And you can also configure the amount of xp you get for killing the mob.
I would also want it to work so that any modded mobs will also get levels people would just need to configure them in using the config file.
These 2 ideas could really make some servers and modpacks really fun. That and its what i personally need for a modpack i am working on that im pretty sure many people will love.