So, I posted this in the New Pokemon Discussion thread...
Anyway, so we've all been thinking that there's going to be New Pokemon in this film, possibly multiple ones. Some people think there's going to be a Pokemon to compete against Genesect in the main film akin to Lucario and Zoroark, others think there's going to be a new Eeveelution in the Mini-Movie.
But what if the new Eevee isn't in the actual Mini-Movie, but in the main film itself? Anyway, my idea was a Dragon-type Eeveelution that's actually created by Team Plasma, possibly Colress due to his research, and is infused with DNA collected from the Legendary Dragon Pokemon. Being a Dragon-type, it's naturally very powerful, and thus considered the apex of Eevee-lution. Of course, in-game, it'd have to have a handicap so it wouldn't overpower the other Eeveelutions, lest the point of branching-evolution would be kind of ruined.
So, in the film, Dragon Eevee escapes, and Team Plasma send the Genesect army out to retrieve it so they can use it for their own cause.