"Another, which was resoundingly rejected, was to unify all leagues behind a front-runner as to avoid fracturing the player pool."
I'm a bit disappointed to read that though I understand many of the good reasons for doing it like this. Nevertheless I think that fracturing the player pool is a very real possibility and the main thing that I don't want to see next fall is 3-5 different leagues all going live at the same time. We should not wait to see who joins what leagues and use that as a gauge of popularity and to see which league to get behind. By the time you let it get that far there could be substantial damage done which could lead to a shortening of the lifespan of our beloved game.
I think we need the leagues that are competing for this spot to present a standardized mission statement/cover letter type document that lays out clearly where they stand on certain issues as well as lets them describe in a brief and direct way their vision for their product and how it would be better or different from some of their competitors. We then need to conduct rounds of runoff elections the results of which would eliminate the least popular choice(s) after which the remaining parties could add to their statements and further plead their cases. This process would be done multilpe times until there are as few options left as reasonably possible. We could even use a form of system like this (https://youtu.be/l8XOZJkozfI) (or not because that might be needlessly complicated).
I should mention that I have no idea what the best way to conduct voting would be as far as making it fair and accessible and logistically practical but I'm sure someone here has some good ideas. The important thing for me is to have as few leagues as possible duking it out for participation come next season. Ideally it would just be one left and we could all give it a fair shake.