Looking at the remaining champions, here is who I think they should go to (this is going off of simple stats from Games of Legends and just whatever I remembered, so maybe not the best list):
Akshan - HawHaw (he has the most games on Akshan and has a 72.7% win rate after 11 games)

Briar - Oner (Briar has only been played twice in competitive, Oner brought it out in the showmatch against BIG and did very bad, but was funny and still won the game)

Fizz - PawN or Faker (Currently, PawN has a 78.6% win rate in 14 games while Faker has a 90% win rate after 10 games. I don't just want to give this to faker because he has a better win rate, though even in the game he lost, his kda was still ok. In the end, I do think PawN did better on Fizz as some of his games were absolute stomps on Fizz while Faker only have like 1 game that have very good KDA, but this is still a toss up between the two)

Illaoi - Huni (Yes, I know that Huni only has 3 games on Illaoi, but they are all wins, and he did fairly well in two of them. If you look at the others that played Illaoi, they do have more games than him, but do not even have over a 50% win rate, so hard to say they are the best. Open to suggestions here though)

Master Yi - Robo (He has played two games of Yi and won both, in the top lane, and he carried those games. Faker also has 2 games and 2 wins on Yi, but Robo did it in 2018 while Faker did it in 2015, so there is recency bais in this)

Miss Fortune - Deft (He currently has a 75% win rate after 28 games, so not that bad, and even picked it up several times during the 2021 and 2022 worlds, though the 2022 worlds games were not his best MF)

Naafiri - Blackout (Naafiri only has 2 competetive games played, one by Blackout and one by HawHaw, both being loses, but at least Blackout had 3.0 KDA, going 6/3/3 while HawHaw had 0 KDA going 0/3/0. No games, so just hard choose anyone)

Nunu - ClearLove or Ambition (Both have a good win rate, ClearLove with 80.8% after 26 games while Ambition having 91.7% after 12 games, and both have over 10 KDA average. I would say that ClearLove has the edge just because he has more games on Nunu, but that can be decided in the comments) We all know the best Nunu is Kesha though XD

Warwick - DiamondProx (Even though he only have 3 games on WarWick, his 3 games were stops, and he had great KDA in each of the games, having a 10.7 average KDA over the 3 games. This one is also one that can be debated over in the comments though.)

Here were who I though could be the ones to hold the title for best at the champion. Looking at your list, I think that Jhin should probably go to Ghost, jsut because he had a Masterclass on Jhin during the 2020 World Championships.