Adding more a more personal experience to ranked
There is nothing but stress and sweat when an average player plays ranked. Ranked is stressful, it's a test to see how good you are against everyone else who plays League. It doesn't have to be this way, ranked can be more fun than just destroying their nexus and knowing its over. Adding a rival system to ranked could make it more enjoyable and engaging by adding something that gives the same longevity as the LP you earn.
The rival system is a vague term to describe a match making system that would occasionally match two players against/with each other. It's not a hard thing to find someone at your level moving at the same pace as you. Often I see in higher elos that some names I recognize will go against each other very often(i.e. S Diana 2 vs Hi im sejong) and these matches may be exalirating to see someone on the other team you've faced before. Your same trick of camping top all throughout the match wont work because they'll be warned same as their aggressive support and duo partner wont be allowed to pull that very very early dragon. The idea of this is to give someone a rival or even multiple people in ranked they'll recognize and feel a personal want to play better against them as well as giving them alittle more pleasure by knowing they beat someone instead of just list of 5 names.