Listen up, normally I'm just a lurker but this ticked me off.
The mere suggestion of this is ridiculous. While you do raise valid points, it does not make the proposed idea more credible. The main and foremost problem with this is that it accounts to all champions, not just newly released ones. As this might confuse you, I'll give you an example to clarify. Recently in my ranked team during championselect the last pick was forced to go support. They picked Morgana, a strong pick albeit slightly unreliable. In game however, the player playing Morgana admitted to not actually having played Morgana ever before.
We lost lane and lost game, but that's not really my point. My point is that there will ALWAYS be players that try out a champion that's new (to them) in ranked. So, banning a recently released champion from ranked play because players can't possibly have enough experience with said released champion is an invalid reason. Completely invalid in fact.
On the other hand, I agree that a player should have some 'forehand experience with a champion before playing it in ranked. Which is why I approve of the champion mastery so much, and I think that part of that champion mastery should be integrated into ranked play (where, for example, a player has to be at least level 1 or level 2 with 16 champions, instead of simply owning them).
Moving on to your other points, this time dissecting buggerinos. Yes, newly released champions may have gamebreaking bugs, but, in fact, Riot actually bans those champions once the bug has been discovered to avoid exploitation! So, banning the newly released champion by default will in fact have an OPPOSING effect, because the newly released champion will see less gameplay and thus the bug might take more time to be discovered, which in turn will cause it to be banned a few more days/weeks later on after its release simply because only then the bug had been found out. Another point you made is, when you keep this in mind, invalid.
I wasn't planning on writing this huge a paragraph, but while I'm on it let me just continue. Another point you made is that enemies do not know how to play against newly released champion (we'll name him Bob). Bob is so strong that he'll easily 1 v 5 the enemy team, score pentakill after pentakill and pushes turrets down solo. Bob has a winrate of 100% and even if afk carries the game with it's passive or whatever makes the champion so strong. Because of this, Bob should be banned from ranked play. Well, in fact Bob should, but not by Riot. Bob is a champion the enemy team can't play against, or doesn't know how to play against. What do you do with champions you do not know how to play against? Exactly: you ban them during championselect. That is precisely what those bans are for. Not to ban just any "OP" champion. There are currently way too many champions that are strong, solid picks (as defined as OP by you(as said by you)) and there is just no way to ban them all. So what champions DO you ban? Why, the champions you absolutely do not want to play against. And not just every new release might bring a champion you absolutely do not want to play against, champion reworks, nerfs and buffs actually do this too.
So is it a ban wasted on a newly released champion? No. Maybe the patch in which Bob is released will bring a far superior threat to your or enemy team as well, and Bob wouldn't be the priority to ban, despite the fact that nobody knows how to play Bob or how to play against Bob.
Enough with the analogy. You raised a seemingly valid point concerning the amount of bans. As I said earlier, there's a huge pool of champions both viable and strong that would be nice not to play against, especially if they counter you or if you don't know how to counter them. So, 3 bans per team might have seemed reasonable when there were 40 champs, but now that there's triple that amount you might say that that isn't reasonable any more. While there does seem to be some logic in that, there's actually an underlying reason as to why it isn't that bad to still be stuck with 3 bans per team. The sole reason is that both teams actually have the same amount of bans (yes really!) during championselect. This makes it so that both teams have a chance to actually pick one of those so called "overpowered" champions, and thus it becomes balanced again.
But Vaatzes I want to play xxx champion that's completely out of the meta and irrelevant and in a position that xxx shouldn't be played! I'm sorry pal, but there's a whole bookwork somewhere out there as to why you CAN play xxx, but why it might be a bad idea. I'm not going to expand more on this other than saying: yes, there IS a meta and yes this makes some champions more viable or less viable.
You also made some points about having to ban specific champions and not being able to ban champions yourself all the time. Those points are plainly ridiculous and if asked I'll elaborate as to why they are. For now, let's just say that A: You can always counterplay every champion if you're skilled enough (unless you're playing at challenger level), so there's nobody forcing you to ban a specific champion, and B: there'll always be a person banning champions, ask them or hope they'll ban wisely. The enemy faces the same problem: they might not always ban the "right" champions, so it's still balanced.
Lastly, the paragraph written in italic is rather absurd. Riot removed free to play champions from ranked because of what exactly? That nobody knows how to play against them? That they might be bugged? That they will "have to be banned"? That players might not know how to play said champions?
Assuming it's the latter, it still makes little sense because of what I've said above. It might be the reason, but it's of little relevance. I could just buy a 450 IP champion and play it in ranked. There isn't really a difference. If you actually answered yes to one of those other questions: congrats, you're talking gibberish.
Thanks for reading all that, or if you didn't, look below. I'd be VERY pleased to hear any reply every one of you has to this, and what you think about the points I made. So long folks!
TL;DR: ALMOST ALL POINTS MADE BY OP ARE FAKENGAI (bear little relevance, have little logic or are complete nonsense). NEWLY RELEASED CHAMPIONS SHOULD NOT BE BANNED.