Other than a few edits and tweaks here and there, I think I've got my 2021 version of TSR, or at least the players' rules, done.
I made a few more changes since my last post on it.
Races got switched around. Instead of the Asian mythology inspired races being variants of the Tolkien inspired races, I made them all their own thing. Only I got rid of Spirit Born, collapsing the best of their special abilities with the Changeling special abilities to have one race. Really, their fluff and most of the mechanics were identical for them. Might as well get rid of one. I also made a bit more variety among the other Asian races as far as what classes they can take, and the max level for each.
So there are now 12 races. I listed Human, Dwarf, Elf, and Halfling as the basic options, and all the rest (Changeling, Dokkaebi, Gnome, Half-Orc, Koropokuru, Kumiho, Tengu, Vanara) as optional demi-human races.
Classes have been set. No big changes, just a few small tweaks to make things interesting or different.
Basic classes: Cleric, Fighter, Magic-User, Thief.
Cleric -- Darkstalker, Druid, Shaman
Fighter -- Kensei, Knight, Ranger
Magic-User -- Geomancer, Illusionist, Wild Mage
Thief -- Acrobat, Ninja, Outlaw
Advanced Classes: Assassin (F-Th), Bard (Cl-MU), Lark (F-MU), Monk (Cl-Th), Paladin (Cl-F), Warlock (MU-Th). I don't have rules for allowing subclass substitutions for the advanced classes. That might be something to put in the GM's book.
In addition, I combined the equipment lists for both versions. The only thing I left out were the special ninja gear (basically copy-pasted from Chanbara). I may put them in the GM book, and let each GM decide which items to make available to players.
I also combined the spell descriptions, adding all the Shaman (Mudang) and Geomancer (Wu Jen/Wushi) spells that weren't already Cleric or Magic-User spells. Previously, I had Druids limited to 5th level spells, but now they get up to 6th, so I rearranged their spell list a little bit, too.
Finally, I had rules for high level characters building castles and getting followers and whatnot at the end of my original document, but I don't think my players ever read it. So I put all that in with each class description instead, and modified versions for the advanced classes. In addition, I had a few notes about magic item creation. I've expanded them a bit, and still may edit them a bit more before I finalize this and show it to my players.
I plan to let my players switch up their PCs to the new rules if they want, or just continue to play the rules they made them under if they find that a hassle, and when they make a new character use the new rules.