I observed that in many mods like N30 Fanpatch by murdilator, they nerf Japan too much, so much so that the civilisation feel is lost.
Inspired by Murdilator's N30 fanpatches and Dragur's AI and various others, I thought why not me? That's why I also stepped in quagmire of modding.
This is just starting of my work, for now I just changed units stats in protoy.xml. In future I'll try to extend this into full fledged patch along with improved AI. I've added some interesting changes too.
For instance, all melee heavy infantry have 1.0 ROF. No one uses melee heavy infantry units like halberdiers/rajputs/warclubs etc., except maybe Aztecs, who use jaguar Prowl knights(they have no other choice!). With this, whenever they come close, heavy infantry beats musketeers and even skirmishers too sometimes. I tried to somewhat break the rock-paper-scissors relationship.
Next biggest change is I've made Mansabdar elephants take 1.5x pop.
Another change I made is, I've increased the siege attack of Sioux Cavalry(except Tashunke) and War club. Now Sioux also can easily break past walls.
Musketeer: Hand Attack:15(13)
Janissary: Hand Attack:18(15) Hand Multlipliers:x2.5(x2.0) and 1.85(x1.5)
Sepoy: Hand Attack:17(15) (mansabdar adjusted accordingly)
Ashigaru: Hand Attack:8(10)
Tomahawk: Ranged attack:22(19)