I appreciate this suggestion, but allow me to explain why I have chosen to do this.
There are two major costs to running this site. The #1 cost is the storage required for all of the data for each league. This cost increases of course the longer a league exists. The #2 cost is the cost required to run the servers to sim the games. But that pales compared to #1. The reason leagues shut down and data gets removed when they get empty is because, without people actively playing in a league, I can't cover the cost to store the data of the league; it's as simple as that. The only viable solution would be to change the model to one where everyone pays maybe a monthly subscription instead of having ads on the site or buying credits, but I believe that would significantly reduce membership and hurt the game as a whole, so instead I have chosen to make it free to play if you choose to do so. The compromise on that point is that, if a league is not being played in, the data for it goes away. The exception of course is that if you have a custom league, that league will not shut down if it is below the minimum threshold, because someone did pay for that benefit.