Pokemon Challenge Y

Features:
All gym leaders are now double battles
All E4 members are double battles
The Champion has a revamped team and is a double battle
From gym 3 onwards, gym leaders will use mega evolution
E4 members will now use mega evolution
Gym Leaders, E4, and Champion have updated AI
Gigalith and Torkoal have sand stream and drought respectively

To Add:
More Pokemon
Editing other trainers (Team Flare, Battle Maison, Route Trainers, etc)
Possibly changing the starting Pokemon or their abilities
Making the mega stones more accessible
After testing for a while, might have to improve some gyms
Whatever your feedback is