Let me introduce myself first. I am a historian graduated from the University of Brasília and History teacher for a few years.
I believe that the construction of a global history could begin with the idea of globalization, seeking to understand the cultural and knowledge exchanges that took place along the formations of human societies. By understanding the exchanges made over time, we realize that we all have cultural aspects that come from several other societies (often very distant) which favors the perception of individuals as "terraqueos" and not only as a member of a culture or Nation.
The construction of such history, however, is rather complex and we would be constantly challenged by each other's historical perspectives, since that the knowledge of most people about history is connected to what they learned in schools and often reflects a national intention (political) of history. (Because history is often used for the construction of national identities and their versions are not always convergent). It would therefore require a good deal of openness to accept and seek a synthesis between the various truths that will emerge.
I suggest that we initially seek to trace some of the oldest societies in the world and from them to seek to trace contacts with different peoples and cultural exchanges and knowledge transferred between it. Perhaps a wiki structure was a good alternative for adding information in a non-linear fashion. In any case there would be a HUGE amount of work to be carried out and it would be extremely interesting if there were contributions from history scholars (amateurs or professionals) from various parts of the world who could add their perspectives and make dialectics.
This structure will attempt to produce a shallow content with many errors, unless there is a systematic research space for people with deep knowledge in the area, but anyway it is a possibility of constructing an overview of the history of peoples.