Each member of the team seems to fill a very specific function that Nightwing has deemed necessary to the success of their mission. His first recruit is Raven, whose telepathic and empathic powers will help them communicate more effectively with terrified metahumans. Beast Boy's powers are on the fritz, which is why Nightwing wants him on the team. Having someone who is going through the same ordeal will help them relate better to their targets. Needing a brilliant mind to work up solutions to metahuman problems, Dick also recruits Natasha Irons.
The only other member of the team he brings on that was on the previous iteration of the Titans is Donna Troy. Given her abilities in battle, Nightwing sees her as one of their heaviest hitters if things devolve into a fight. Her leadership, training, and tactical skills will also come in handy as something of a field leader. Despite Donna's reluctance to accept such an invitation, she ultimately sees this as a means to change how the Justice League sees her. By doing some good, maybe she can finally figure out who she is now, and who she will end up becoming in the future.
Nightwing fully intended to stop there, but the Justice League had other ideas. Since they didn't approve of the last iteration of Titans, this new team will have to be supervised. Martian Manhunter assigns Miss Martian to the team as their Justice League liaison, or as Raven so eloquently puts it, their babysitter. As well organized as this group may be, it seems there will at least be some conflict in the works. Can the Titans put away their pride and accept their new member so they can save the world? This group is going to have their work cut out for them.
Infinite Possibilities Lead to Infinite Threats
Since the Source Wall has been broken, new threats are coming to Earth, and the metahuman population is increasing. A group of heroes will need to rise up and meet them, not just to fight, but more importantly to help. These people are vulnerable because of their dangerous powers and how society will react to them. Nightwing's team of Titans are looking to help in the best ways possible, but that doesn't mean others are looking to do the same.
Someone like Brother Blood only sees new assets to control. Thanks to his connection to the Red, and the Earth's morphogenic field, he understands that big changes are coming to the planet. He believes the universe is creating new weapons for him and his followers to harness in order to seize more power. The Titans are going up against their ideological opposite, but they will also have to be prepared for an even bigger threat than they could have ever possibly envisioned.
The energy coming out of the breach in the Source Wall is affecting the entire DC Mutiverse, not just the reality of New Earth. That means new threats are popping up on dozens of different Earths at the same time. If Brother Blood finds the means to harness these new abilities, Nightwing and his band of junior Justice Leaguers are going to be out of their element very quickly. Will the Titans need help from the big guns, or can they stop things before they get out of hand? Well, that's the question, isn't it?