Promotion series?

Im a student from Finland, and I study alot and in between my studies I like to play League of legends because I think its a really fun game. I planned out that today on saturday 15.9 I was gonna play and hopefully climb. Everything goes as planned and im in promos. I loose one of my promos and think to myself that ''Can't win all games its fine next game im just gonna win and succesfully complete my promos''. So in the next game same macthup, goes the same and we are ahead with a good late comp. But suddenly our jungler ragequits. Im always /mute all but my teammates tells me he ragequited. And now we of course loose the game and with the game I loose my promos and fall down on 70 lp, which means that I have to play 2 more games to get into my promos and then have to win two MORE games to get to the place I would have been if I only would have not had bad luck. My point is 5 games worth of my valuable time got trown away because of a little bad luck and its probably going to go another week until I can play again. I always imagined a ranked system where under 100lp would be bronze V, if you manage to climb up over 100lp you promote to bronze IV and on and on it goes. With this system the whole ''a leaver in one game deletes the past 5 games'' wouldn't be possible. If someone ragequits we could just open and go next and would barely loose anything.