Actually the way assists work in Nitroplus Blasterz is pick a character, then pick 2 different assists to team with them. This way, like marvel, you can take one character and back them with two assists. Its not a tag game so this is how Nitroplus handled it and their method of balancing assists since you can pick any two is to have very different cooldowns for each one.. Dengeki only let you pick one assist, but the thing most people didn't know about from trailers is that each assist had TWO different moves. A neutral one and one that can be done by hitting a direction and assist. So Dengeki also had two assists on deck, but since you couldn't choose any two you wanted and could only choose one person and the two moves they had you needed to be more strategic in who you chose in case you needed their "plan B" assist.
Fun Fact about N+...YOU CAN HAVE TWO ASSISTS AT THE SAME TIME.
N+ is a 5 button fighter L, M, H, escape action, heavy action.
Here is a system rundown vid so you can get an idea of how it is
The Heavy Action button stuff like Guard Crushes, Wall splats, and all that is actually not entirely new for EXAMU. Arcana Heart uses much of this. In lieu of the evasive stuff like dodges and air dodging it used a homing dash button, massive screen height, steerable homing dashes, and a shitload of dash cancels and such. In other words, it made you have crazy air mobility instead of dodges in Arcana Heart. I highly recommend the title given you can equip an entire character's worth of specials, supers, ultras, custom xfactors and passive abilities onto any character all balanced via changes to your def/atk.
Here is the Arcana Heart 3 Love Max OT as a quick reference to character documentation and Arcanas. Its on steam with region free online matchmaking and its pretty great too.
I haven't gotten to play N+ yet and wont for a few more weeks. From what I've seen it seems worth it. Very footsie heavy. I also highly recommend Dengeki Bunko Fighting Climax Ignition to folks. It really takes off once you get down the rhythm of doing EX and Ranbu a lot to build blast and then using Blast meter to "xfactor" over and over to gain meter and bonuses. Trump cards are also hype. Not as extreme as HD combos, but they let you go crazy out there for a period and every round you lose you gain a trump card back meaning you can go ham in round one and use both trumps, lose and still be good.