How new account should work especially in Rank
All new account, whether it's new players or smurf, should start all their game at least Silver if not Bronze.
Why make new player start Bronze/Silver, because they're new no shit. Unless you want new players in your game in Gold and Plat, maybe even Diamond as well.
All new account should not be able to be place in Gold, especially Plat whether they get 10/10 in Placement Matches.
Why? Because this encourage Players to keep smurfing if they know they can easily place high and skip through division. Some of you may think, well if they can easily get out of low elo Rank fast then it's ok, but no it's not OK. Because of this reason, legit new players or Bronze player who make new account are able to get into matches they shouldn't be in because they ruin the Match Making Balance base on Players skill rather than the Account MMR.
Why all new account should not be able to be Place Gold right off the back? Because Gold is the goal for every players to be able to receive their "End of Season Reward" New Players should play the game to earn it, not get lucky to easily place in Gold right off the back to earn the Reward.
All new account should have a "Smurf Placement Test" before they start their actual "Rank Placement Matches"
This wouldn't make sense, but there is no way for Riot to stop people from smurfing ever. And also the fact that smurfing is allow -- Smurfing is just not allow "Competitively" said Clash Mode -- Smurfing is just not allow for the purpose of "Boosting other's Account"
How does this "Smurf Placement Test" work? Well instead of playing 10 whole game, it should have 3 Matches where the Players will play to see how his performance is, I'm pretty sure Riot has an in game system to see how someone perform on a Skill Base and not just base on whether they lose or win.