Turns out all aggressive and neutral mobs, but not passive mobs, nor dropped items, have an attribute that determines how much damage they do! using this, I created the exact same system as before, but ONE TENTH the size, if not smaller!!
Thanks to this, I can not only make a custom aggro range (default for everything except ghasts is 16 blocks, ghasts aggro range is 100), but I can also improve Minecraft's native hiding mechanics. I intend to improve the detection of invisible players so that instead of seeing invisible players at 13 blocks, it instead will hopefully be 8 blocks.
Also I started working on a mechanic that reduces aggro range if the mob is inflicted by blindness - meaning applying both should reduce aggro range to about 4 blocks. Currently I'm building an "RPG Stats" module as a proof of concept. It tracks Strength (damage dealt), Dexterity (arrows fired), Constitution (damage taken), Intelligence (books crafted, maybe add potions drunk, and enchantments made?), Wisdom (mobs killed), and Charisma (time spent sneaking).
In the order above, the benefits given are:
Alternating strength bonus when not holding a bow and crouch-jump boost.
Alternating weakness to enemies when holding a bow, and run-speed boost.
Increase max hearts by two, 5 times (maybe 10 times?).
Every level up in Intelligence gives the player a Bottle O' Enchanting, and is an exception to the Occasional Skill Rule.
Killing enough mobs will grant you an incremental luck bonus - which is like the looting enchantment (except it also works on fishing and dungeon chests, probably stacks).
Sneaking bonuses are as follows: invisibility when sneaking, night vision (make toggle-able somehow), make enemies glow when near the crouching player, blindness on enemies and increase glow range, wither enemies that get too close (need to add an exception for neutral mobs who aren't angered) and increase glow range.
Occasional Skill Rule: each new skill in any given ability is gained at level 16, 32, 64, 128, and 256 respectively. Strength levels up every 500 because it scales faster due to the bonus gained. Dexterity levels up every 16 times a bow is used. Constitution levels up every 100 damage taken (for sake of comparison that means to get the first pair of bonus hearts without healing wounds, you'd need to die 80 times). Intelligence levels up every 10 books crafted (because leather). Wisdom levels up every 100. Charisma levels up every 1000 ticks (50 seconds) you spend crouching.