With the limited availability of Gyms, I've been thinking of some creative original League ideas. They may not be necessary, thanks to the Dojo League and the inevitable Isshu League, but I thought I'd put one of my ideas out there, in case it's interesting enough to implement.
The idea is simple: A league of 6 Gyms, each of which, instead of representing one of the elemental types, represents one of the six stats of Pokemon: HP, ATK, DEF, S.ATK, S.DEF, and SPD.
The requirements for Pokemon for each Gym Leader would be simple: Every Pokemon of the SPD Gym Leader would have to have a Base Speed of 120 or more. Looking at a list of Pokemon by Base Stats, the 120 Standard would work for all Stats (with the possible exception of HP).
In any case, it's just an idea I had. It's up to the community to praise it or shoot it down, and up to the staff to decide if it's even warranted.