We a there are perhaps two main reasons why collaboration is key to doing this successfully. First is the issue of quality, as touched on above. Having more than one qualified individual working on a project makes error correction easier, earlier, and more consistent. No one does perfect work, not even the best scholar. In good collaborative efforts it can almost seem like you have multiple editors working for you to make sure your work is quality.
Sharing the workload is also important because there is so much to do. Just in the realm of the study and availability of primary sources, how much time will it take to get everything that would be useful available for anyone to use? How long will it take to prepare the Old Testament Pseudepigrapha, or the same for the New Testament? Editions of all that in their various languages with good, modern translations? Other works from the time period? All the works of Classical Greek? All the important source documents of the Early Church? That will take a great deal of time. But what about secondary materials, study aids and analyses of those works? That will take even longer. This is a task much bigger than any single person or group. The industry, the students, the scholars all need to participate. We all need to move in this direction just because of the mass of material that needs to be prepared.