Edit: Here we go again. I can't stop being ninja'd. Have pity, milotic's base speed is just 81.
Kecleon. It actually has a big and really exciting move pool, and the protean ability, I think it could be great with a 2nd stage evolution with higher stats make use of its tools. Also with an evolution Kecleon could be a decent eviolite user, it's special defense is already high.
The regional Sunflora. I think it would be pretty cool to see it represent the flora that grows in another region.
Terastialization or Z moves?