New Ranked System
I'm tired of waiting for Riot to implement a new ranking system, so this is how I would do it.
FIRSTLY Make the Champion Mastery system more strict. As in, it's a lot harder to get S+, and a lot easier to get D-. The reason will be listed below. SECONDLY Unify the divisions. For example, Bronze 4 shouldn't have things like "Draven's Dominators" and "Hecarim's Hunters." Just unify them into "Bronze 4." It helps simplifies things, and the reason is listed below.
Ranked System First Make the amount of LP gained/lost dependent on 1) Whether you lost or won and 2) Based on what your performance on that champion was. Examples: (This is a Gold game. Rewards should be less in Plat+ and losses should deduct more too.) You won a game with a S+. Good for you, but since it's easier to get S+ on the winning side you get +20 LP! You won a game with a B. Since this is the middle ground, you gain the normal amount of LP! (10) You won a game with a D-. Although you probably got carried, I'm not sure so you get +5 LP! You lost a game with a S+. We know that you tried, and did good, so you lose only 10 LP! You lost a game with a B. You're average, so you lost the normal amount of LP! (25) You lost a game with a D-. You probably sucked, so you lose more LP than usual! (40)
What does this achieve? People who do well in their games will be able to climb faster than normal, by losing less and gaining more. The same goes for people who are bad at their games. These people will gain less LP than normal, and drop divisions faster, reducing all trolls and intentional feeders.
Second Remove the promo series. They are a source of frustration and allows others to troll them. Instead, do this: Jumping up and down divisions is based on your win-rate in that division. If you have a win-rate of 54% or more in a division, you are automatically placed into the next division. If you have a win-rate of 46% or less, you are automatically placed into the previous division. In order to prevent people from having "lucky" games, you must play a minimum of 13 games (if you win at least 6, you will stay in that division until you either get a win-rate of less than 46% or more than 54%). Also, in order to challenge the player and see if he/she really deserves to promote/demote, players with 48-52% win-rates are matched with people from the same division, people with 52-54% winrates are matched with people from the same division and one division upper, and people with 46-48% win-rates are matched with people from the same division and one division lower.