Nothing is more irrelevant in college sports than last year. This year's team has no control over last year's ratings. Obviously they impact results, but they're not quantifiable. Also not reliably reported and may change during a game. Yes, they appear in a box score, but sometimes even those get changed after the fact.
Teams have some control here.
There are endless numbers of rating systems that could be devised dependent upon what the creator chooses to do with this information. I will not attempt to answer any of these questions. I will however attempt to evaluate the nine current ranking systems based on known information and how they conform to these standards. They start with a preseason expectation. This means that the polls are essentially a measure of which team has the longest winning streak.