Crisis Core Final Fantasy 7 Reunion will feature a new "menu-based battle system" that seems to be reworking the original's DMW system.
One of the most unique things about Crisis Core's gameplay was its real-time battle system, which let players run around the field and use abilities and attacks when they liked, selecting attacks from a menu. It also featured the DMW system, which essentially made added slot-machine elements to gameplay to give the player random buffs depending on which character's faces appeared on the slot machine.
Both the real-time combat and DMW systems were pretty polarising features of the original Crisis Core, with some players loving how unique they were, while others thouhgt that that the DMW system in particular made combat too focused on luck. It looks like it'll be changed somewhat for Crisis Core Reunion, however, as a new Tweet implies that combat has been reworked.
The Final Fantasy Twitter shared a few new images of Crisis Core Reunion while stating some of the changes that are being made to the game, including mentioning that it'll feature a "new menu-based combat system". Square didn't go into detail on what exactly that means, but it's clearly reworking the combat in some regard.
Interestingly, the gamepaly footage that we've seen of Crisis Core Reunion so far doesn't seem to have changed things all that much. The same menu-based attacks are seen in the lower right, and the DMW system can still be seen in the top-left corner.
As it stands right now, it's not clear what exactly is being changed about the combat system to make it more "menu-based", but it looks like Crisis Core Reunion is changing a bit more than we had anticipated.
Another big change being made to Crisis Core Reunion is the addition of full voice-acting to scenes that were previously text-based, as well as new new background music arrangements by Takeharu Ishimoto and improved movement and control across the board.