As I am sure you all know, Rick and his group have found salvation within the walls of Alexandria. Pretty great, right? Maybe not so much. We know that Deana has stated that she wants Rick's group to help them "survive". Though one would assume she means that she wants their help with the fundamentals of living life during the zombie apocalypse, there could, in fact, be a deeper meaning.
When Aaron and his partner, Eric, are watching the group (we know it was for a "few weeks" but we cannot really be sure of that time-frame), I would imagine that they heard and saw them do some things that a so-called "normal" person would not do (like eat some dogs). Obviously, this has something to do with the fact that the Alexandrians have never really lived outside of the walls, which also means that they may have never had to do what is necessary to survive. As of now, we, as viewers, know that the majority of the people living in Alexandria have been there since the beginning of it all. On the opposite side of the spectrum, we know that Rick's group has been through it all. They have never had a sense of security during the course of the show. Sure, there have been times when they have been considered more secure than others, but they have never had the luxury of living behind steel walls. During our time following the group, we have seen some pretty gruesome things (i.e. walker deaths, human deaths, etc.).
Through it all there has been one consistent variable. Order. Whether it is Rick himself or a counsel of other members, there has consistently been a sense of order amongst the group. This obviously makes them an asset in multiple ways. They are more than capable of survival and doing what needs to be done in order to ensure that survival, but they have maintained a sense of order through it all. Now, obviously Deana sees that as something desirable for their community. But what if there is more to it? What if there is another reason that she wants these savages to be a part of this innocent community?
IN MY OPINION, THIS IS THE REAL REASON DEANA WANTS RICK AND HIS GROUP AT ALEXANDRIA:
She knows about another group (or groups) in the remote area. There have already been hints dropped that the Wolves will be the first group the Alexandrians run into. I believe this to be true based upon the fact that walkers are turning up dead with a "W" carved into their foreheads. Maybe, maybe not. Only time will tell. There was also a note written on a wall that read "Wolves not far".
If you are a fan of the graphic novels, you also know that there are other groups out there such as The HIlltop, The Saviors, etc. I think Deana knows about the threats (obviously, not the Hilltop) that are lurking around their community and she wants Rick and his group to be there when the shit hits the fan. We know that the group is well equipped to take on other survivors, which is something that we have seen before. Deana is putting members of Rick's group in positions of power in order to have the other members of their community look to them as authoritative figures and/or people who can be trusted, though they are new to the community. I believe Deana knows that Rick and the group lead by example, for instance Abraham saving the woman at the construction site while everybody else had ran away (mostly). The fact that Abraham went back and nobody else went with him shows that the people of Alexandria are not ready for a confrontation. We also find out that Aiden and Nicholas left their friends to die on a supply run because they were too scared which further strengthens the fact that the Alexandrians are cowards. Deana understands that her people are weak and Rick and his people can change that. The walled community might be safe from walkers, but it is not safe from people.