Are the two ranking systems designed for the same purpose? It seems to me that a system designed to find a winner for a 'season' is a very different thing from a system designed to identify the best players (and perhaps be used as one of the criteria for who gets to go to any invitational tournaments).
The latter should ideally look back over more than one year. In some ways we are back to the luck v skill debate, and the definition of the 'long run'. In a single year, luck will still play a significant role, even under a system designed to reward every advancement from a table, rather than just final and semi-final appearances.
For a generalised - who are the current best players? - ranking system, I'd go for something like the accumulated points total over the last N tournaments which they entered, where N is a suitably big number to define the long run (maybe 100?). To stop people retiring on top and staying there, it'd have to be the last N tournaments held within the last M years. For active players, there would be a rolling process - each new tournament they play bumps the oldest one out of their set of qualifying tournaments; if they did better in this one then their points total goes up, if they did worse then it goes down.
Obviously there'd be the question of what happens if you don't have N qualifying tournaments under your belt (as would be the case during the startup of such a system, or for someone who hasn't played recently and often enough to maintain the 'N tournaments in M years' qualifying record). In that situation, I suppose you either simply don't have a ranking, or it is in some way flagged as 'provisional'.