I didn't concoct anything.I really think you've concocted a pretty convoluted solution to a problem that won't really exist by the time this all comes to pass, and described all the possible complications of same. I'm pretty confident it's not going to be nearly as bad, and even if it were, it would only be transitionary while all the leagues that matter got in sync.
Another poster said if there were groups of players BY and SY the easiest way to make the rankings app work without changing anything is an additional break out of the data between BY and SY per age group.
Instead of...
B2010
B2011
B2012
It would be...
B_BY_2010
B_SY_2010
B_BY_2011
B_SY_2011
B_BY_2012
B_SY_2012
What I wanted to do is add a power percentage to the teams in the league that were 6 months older. This would allow all all teams to continue to be viewed in the same age group. (Ie B2010, B2011, B2012)