What do you mean?
You know how Greninja was chosen early on even though Gen 6 was still in production, since X and Y were slotted to be out a year before Smash 4? Sakurai and his team were sent copies of concept art and other design documents to build Greninja with to make sure the portrayal was accurate.
But here's what no one ever mentions:
there's no way Greninja was the only one they looked at. They wouldn't have banked on just one option. They would've had multiple Gen 6 mons that they chose from, and then decided Greninja had the most potential of them.
Who's to say they might not have been interested in a second one of them, and said second pick was just overshadowed and left on the cutting room floor only to be brought back once DLC went under way? And when you consider Delphox is a starter, a firebender (a popular element), and a mage (a
very popular character type), it makes you wonder.
...Oh, and Delphox is also Junichi Masuda's favorite Kalos starter, so if Sakurai asked he'd be on board with it.