They won’t be working from any sort of shared home base at the beginning of the movie, but assuming that they’ve successfully fought off their adversary together by the end, the building could be something Bruce Wayne had constructed for the new team.
If Joss Whedon is looking to add the Hall of Justice, we’re guessing it will be for a major finale scene that is being added.
We have to say, seeing the assembled heroes standing in front of the Hall of Justice as a final shot sounds like the perfect way to end the movie.
Clearly, the purpose of the movie is to bring the characters together and to get them starting to work together.