Okay, we currently have 130+ Champions. What kind of Champion would be a good and unqiue addition?
Riots design policy is to make champions very unqiue and distinguished. They want to fulfill the fantasy of a champion for everyone who plays their game, so they keep releasing very different champions every year.
Even so, they surely didn't fulfill every fantasy of every player yet. So if you look at the whole roster, what is missing in your opinion?
Personally for me i always wanted to play a sheer-force-barehanded-fighter Champion. Yes we have Lee sin, Udyr and Vi, but they never quite hit the mark for me personally.
Vi's personality is obnoxious , as much as i tried coping with it and i can't even see the muscles on that brawler woman, why cant she have a buff body AND giant robo gauntlets,why does characters like her always have to look like they never touched a dumbbell in their life? A champion like her needs to make me think: "Wow what a powerful and strong woman". But instead it's just "....meh an average person with robo gauntlets that define her strength solely." So to me, IMHO, she doesnt really fulfill the fantasy she is supposed to fill.
Furthermore all the unarmed martial artist champions are mainly viable in the jungle only.
Whenever i see Malicious Metal's posts on these boards, i see a person who has found HIS champions, the passion is simply astounishing and so intense. I can't help but get envious, but also impressed for the effort he puts into his beloved champion. I have played League of Legends since Hecarims release (1st Quartal 2012), during that time a vast variety of champions was released. But at times, i feel like Riot tries to make champions too unqiue, prime examples are Tahm Kench, Illaoi and possibly Taliyah. Are they unique? Yes, but do they work in a healthy way in this game? No. Not every champion has to be an absolute supreme Hipster.
The roster should be filled with a vast variety of unique cool and distinguishable characters, not a Freak Show of champions that doesn't even make sense. A catfish-toad that licks people and takes them in his mouth, was so forced into this game that he doesn't even work properly and a cosmic dragon god that is lorewise so powerful that he can literally kill all the other champions with a flick of his finger and possibly even Runeterra itself. What's next? The creator of the universe or even existence, with the physical appearance of a gigantic cosmic bonobo monkey? Okay, i exaggerated, but hopefully you get the point.
Oh. Uh...

looks like a cowboy but without the personality and weapon
looks and talks like a cowboy but without the weapon
looks and sounds nothing like a cowboy but has the weapon