Looks awesome, but I'm a bit worried about the whole "promotion series" concept. It sounds like once you're ready to advance, you need to win 2/3 or 3/5 games all at once, to determine your advancement to the next tier. In solo queue, this will be a huge mess. Imagine having played 4 of your 5 promotion games, and you're 2/2. The last game determines your advancement to the next tier, but then someone plays really badly and costs you the game, ultimately failing you to reach the next tier, and you need to obtain your points all over again. I can see even more raging in solo queue now, since so much more can be put on the line. :/
Additionally, it sounds a lot more grindy to get out of a tier. 100 league points for 1 division, and 5 divisions? This could take forever to rank up.
By putting so much on the line of a single game to advance, you're basically asking for more raging and bad sportsmanship.