One practice that we follow is decoupling common configurations into a separate AEM Maven Conf Project. You will find run mode configurations, dictionaries, replication agents, etc... Ensure filters are removed from your A & B project.
If any developers want to change common configurations, they can simply make changes to the new AEM Maven Conf Project. But beware of your authors. In many cases, authors would like to manage dictionary keys themselves, so you need a strategy for this.
I hope this helps.