The problem isn't the ratings system, but the lack of trips. You shouldn't look at it from the perspective of that Ross "got" to avoid playing Nationals and win his trip, but that he had to. There were a ton of 11-14 and 10- players who also skipped playing at Nats to secure their trips. This is where the injustice lies.
It is a terrible system when multiple players independently realize that it is in their best interests to skip the biggest and (arguably) most fun Pokemon tournament of the year. People shouldn't have to choose between Nats (and a bunch of other tournies) and Worlds.
The solution?
Increase the number of trips! I heard Nintendo spent $18k on those inflatable things Pram tried to fight for some beer money. That was enough for at least 50 more trips to worlds. If you do the system based on rating, but have it include a HUGE number of people, you avoid players skipping/dropping from tournaments just to make it to another. People should always have it in their best interests to play in as many pokemon tournaments as they want.
If you increase the invites back to 50 (or ****, 100!), you make it so everyone plays again. Why? The top players won't drop enough points to fall off the map, so they don't mind playing. Furthermore, the lower-ranked players can't risk not playing lest they get passed, so they play as well. In the end, you have people actually showing up to tournaments again. That's what PUI should be supporting.
Going to worlds shouldn't be dependent on which tournies you drop or which side of the Nats bracket you're on; it should be the best players. Furthermore, the system for determining the best players shouldn't punish them by making it in their best interests to not play the game they're the best at.
It just makes sense.