Pros: More than 6 bans
Cons: Implemented in a way such that a large subset of champions will never again see the light of day.
Seriously, I don't see what the difference is between implementing the new ban system and just removing champions like 
from the game. The end result seems like it will be nearly the same either way.
NinjaGuy692 votesIt was inevitable. When Riot allows toxic champions ( ,
, 
) to remain in broken states without addressing them and then gives us more bans, the players will address the balance issues themselves by permabanning said toxic champions until Riot does something about them. What did you expect was going to happen when 10 bans hit live?
TheGrot1 votesBy my definition of "toxic," those are not toxic champions. A champion is toxic when it is seriously lacking in counterplay. Those are just champions that are frustrating for people to play against because of lane phase, and a lot of people don't know how to play against them. Do I enjoy playing against Darius or Yasuo or Fizz in lane? No. Do I think they are op and need to be banned? Absolutely not. Do I think my chances of winning will change in any significant way if I do or don't ban one of these champions? No.
NinjaGuy691 votesProbably not by your definition but certainly by the definition of many other players. Just go on OP.gg or any other data aggregation website and look at their ban rates.
TheGrot1 votesI don't think you read what I said. A large majority of players do not enjoy playing against X champion. Because of this, a large majority of players ban X champion.
My point: These champions are not "toxic" because other people do not know how to play against them or do not like playing against aggressive early game champions.
Define "toxic". I'm pretty sure my definition is pretty close to what most players accept it as. You are probably confusing it in this sense. Here's how I use the word:
Playing Hecarim against Darius top lane: "Ugh, this match-up is so incredibly toxic" (Note, I did not say the champion was toxic. I said the match-up was toxic, because there's pretty much nothing that you can do to prevent yourself from getting stomped)
Playing against Xayah with any cc support bot lane: "This champion is so incredibly toxic" The champion is toxic because the same thing is going to happen no matter what match-up there is bot lane. Similar thing with Camille when she first came out.
Ok sure but why1 votesThe difference is I'll never have to play against Kennen ever again
TheGrot2 votesOkay yeah. That doesn't make it conducive to game health though. Just auto removing a subset of champions because people don't like playing against them doesn't make the game healthier. If anything, it makes things worse.
Will I be auto banning a champion 
almost every game? Yeah, probably.
Is it because that champion is OP? No.
Is this champion getting auto banned every game conducive to game health? No, I highly doubt it.
Does me being able to auto ban this champion every game make me at least a little bit happier? Yeah, I suppose.