Lorenzo
In my opinion...
All players (even pro and elite) must be kicked off after 30days of inactivities.
All Leages with only one team or without team for 30 days have to be deleted.
The game is full of empty championship
Well, for the players, in my opinion is ok as it is at the moment. If someone has managed to get to the pro or elite ranking it means that he/she has been a fairly active racers and deserves a little more of credit (stuff might happen in life and not everyone might feel comfortable with telling this to people that they do not even know). In any case if someone is inactive over a long period he/she will end up being relegated and, once in the rookie tier, will be kicked out anyway. Also, the creator of the league can kick out anyone at any time, if this gets a problem.
As for the league, this is already happening, but has to be said that the reason of having empty championships is that the current rules, in my opinion, push people to gather to the few populated championships available, rather than to spread out and fill in the empty leagues.
Also, those empty leagues in the past were useful to people for making experiments, getting more confidence about the game or simply finding temporarily a quieter and more relaxed environment where one could compete without having to be active every day. Then, when one feels more comfortable, he/she could have been joining other leagues or, as happened to me in the past, little by little someone might have joined the league and filled in again the championship.