1. Seperate issue.
2. Not applicable to avarage players.
3. Not relevant.
Also most games are supposed ro match to to players with similar skills, or you can choose this manually.
I mean I get your points but none of them are the same thing as m+kb vs pad.
1) It's not a separete issue at all if you have in same game playstation players and pc players. Based on your own words the pc players have the edge due to the use of keyboard and mouse.
2) Every single player will do it better with better hardware simple as that. So yes it creates imbalance. At the moment when you admit that keyb + mouse offer an advantage on consoles you admited that better hardware offers an advantage. Check the internet you might find out that even first time players when put on better hardware performed better in shooter cases.
3) It is relevant because even 20 ms better reaction times on average makes the difference between you dead or you alive. And yes the age of players generate imbalance.
You started the talk about imbalance I just pointed out that the imbalance is there no matter what you do.
And I have one better. The ping and connection stability is another case of imbalance. (Sure you can start with buy better internet, but that won't change the ping between a player that is 2 km from the server with direct link to it and one that is 4k km away from the server that well will have to deal with the increased ping due to distance and hops.)
Show a system that is actually capable to properly evaluate players skills. So far I was unable to find one that works properly and there is no way to actually implement a proper system unless the match is 1 vs 1 and doesn't stay at all in rng and both players have similar reaction times (or reaction time have no impact on the game), use similar hardware (or the hardware have no impact on the game) and have same ping (or the ping have no impact on the game) and internet connection stability.
In a shooter case your reactions time, the hardware that you use, your ping to server, your internet connection stability count a lot. In an online shooter there is no way to eliminate imbalance no matter what you do.
If you match a player with 20 ms ping with a player with 120 ms ping it's expected that the player with 20 ms ping to win. He's just gonna see first the one with 120ms ping.
Want to fix this? Good luck, the game will become a lag fest caused by the players with high ping/unstable internet connection. So you tell me how you properly evaluate those players skills? Because in your evaluation you will evaluate one of the player ping and the result is not his real skill level because when he will move closer to the game server (lowering his ping) he will just spike in his skill level not because he improved but because of a better internet connection.
The elo used in chess works in chess fine, but if you try to implement it in pc games it will most likely fail.
Chess is 1 vs 1 game and in normal conditions there is no 3rd person interfering. This is actualy one of the most important differences.
Proper chess is played face to face. There is no hardware involved to affect performance, this is another important difference.
You can't implement the elo from chess in Heartstone for example. Yes Heartstone is a 1 vs 1 game, but in Heartstone if you spend $ you can just have a better deck than someone that just doesn't spend a single coin in it, so if you just try to use the elo from chess in Heartstone you are also evaluating the $ spend in the game by a player not only his skill level. With the guides for decks you don't really evaluate a player skill level because picking the cards for your deck is also part of your skill level.
And Heartstone is an easy case because it doesn't depend on ping, it's a 1 vs 1 game and you can play it with 20 fps. It depends on connection stability an the money you spend in the game.
Teamfight Tactics it's unfair by design the rounds when you have to wait for others to pick a champ makes if unfair because they have the chance to pick a better champ or/and better item before you, not to mention the rng that can easily make you unable to build anything in that game. The rng applies to Dota Underlords. And those are 1 vs 1 games.
In a free for all game if I'm allowed to play in a party with a friend or more then we can act like a squad and happy kill around players because we are more. You can say it's matchmaking manipulation. Is it? When the game allowed me to party and play in same instance with my friends the game developers were fully aware that my friends can just let me kill them to boost my ranking and that we can squad it to be the last ones alive. So there is no matchmaking manipulation at all cause the developer itself allow it to happen. (Sure you will say that your friends lose ranking, sure but maybe they are just better than me and want to boost me and they will recover the ranking when they play without me.)