I came across these pics on Tumblr which made me believe trainer customization was confirmed to be a no-show in the games:
(spoilered because I know some like to avoid spoilers)
I also quoted some of the post, courtesy of Tumblr user
choice-scarfed-umbreon who provided the pics in the spoiler tag just above:
"Also the footage it was announced in seems to make it look like character customization is no longer a thing, since the female trainer's picture on the battle screen appears to be a ranger, but when the battle begins, she's just the default female character. Which is rather disappointing. Fans loved the ability to customize their characters, it was a huge selling point. Plus the ability to do so is already in the engine they're using now, I just don't see why they wouldn't add it. But that one second seems to prove that it's not in there anymore. But there was also the ability to set it as a character in X/Y, so it's not completely off the table, it's just unusual that they'd do this."
I think it's a disappointment to many, but I think what Game Freak were aiming for here was that they wanted to stick close to the originals. This is a remake after all.