Just recently, something very interesting was found among the files for the alternative clothes used in the rhythm game Persona 4: Dancing All Night - the spin-off of the popular RPG series...
Those are the clothes used by the Persona 5 character: Caroline. It's not being used by the game currently, which is a real waste!
As of now, there's no confirmation that the 4th and 5th game take place in the same universe, but one way or another, this probably doesn't mean that Caroline was supposed to be playable in Persona 4: Dancing All Night.
Given how it's normal to change the clothes of the playable characters in this rhythm game, this outfit was most likely to be an alternative costume for one of the currently available dancers. And by the size of these clothes, a very possible match would be Nanako Dojima.
Why was this feature left unused? Nobody knows, but maybe this is to be a DLC planned to be released sometime after the launch of Persona 5.