Trust me, I don't know enough about Progressive Leagues to ever think about running one, but this theme had me thinking this evening...
I wonder if anyone's ever done a "reverse" Progressive? In other words, take two years in the middle somewhere - say 1955 and 1956. Make a list of all eligible players who are eligible for those two seasons. No clones though - only one of each. In the initial draft, you can choose just like a regular progressive draft, drawing from each of the two pools. The next season, for every player that was drawn from 1955, you go backwards and get his 1954 season (and then every season before that and before that, etc.). For every player that was drafted from 1956, they go forward like a regular progressive league draft does.
Seems like it would be some interesting drafting strategy, eh?