The new Persona Q allows you to play as characters from booth Persona 3 and Persona 4 with the same characters but not the same gameplay. To be more precise not the exactly the same gameplay. To start with the rule about the main player is not the only one who can carry an extra persona. You can now equipped a sub persona to the others characters in you five person party. Also there something called boost mode where once you enter it you sp will cost 0 and you can do all out attacks which can be followed up. Nothing mentioned about combination attacks (Darn).
Article:http://www.siliconera.com/2014/02/20/persona-q-shadow-labyrinth-characters-can-use-personas/
As always thank you for reading.
