One idea I have regarding the storyline of the upcoming multiplayer game would be:

Given that in order to make the UI make sense where the Focus has played that role, being set in a time and place where knowledge of its capabilities would be somewhat limited to the player, maybe the storyline could be set in between the 2nd and 3rd games where Aloy would reach out to the Hunter’s Lodge and tell Talanah about everything, and explain what was going to happen and gifting her a large cash of Focuses and would enlist her help to gather information and support to help with countermeasures against NEMESIS, with the Aloy camno being in the form of a series of introductions videos about how the Focus works among various special events that could slowly move the world closer to Horizon 3

I could also see the possibility that given the rules of the Hunter’s Lodge about how one becomes leader by in part defeating a particular powerful machine, that some people within the Lodge would seek to give Aloy a greater influence, potentially leadership, being willing to skip the traditional way within the organisation due to having recently defeated a Metal Devil in the Burning Shores once word reaches them, something that she would most certainly reject given her character and not wanting to upstage her friend, though she might be reluctantly persuaded to accept a greater role as potentially a larger part of new recruits would join because of her, something that she would not be comfortable with being venerated even for her hunting powers, with the multiplayer game doing some of the heavy lifting regarding the set up of Horizon 3 in how the world would prepare for NEMESIS, that for new players could be condensed into a series of datapoints among other things

Another potential storyline might be:

As for the timing of the upcoming multiplayer game and the potential overlap with Horizon 3, to prevent any timeline issues, if knowledge of ZD had become commonplace after the events of the third game among the general population with NEMESIS already being defeated, though way of Aloy needing to partially reterraform parts of the world in an effort to heal any damage caused by NEMESIS

With the game starting in the aftermath of the final battle and to repair such damage caused by NEMESIS, potentially being to great or so obvious that such actions would that even for Aloy and GIAI would require additional help from the rest of the world or not being within the normal limits of the machines that would make their activities not work if humans continued to hunt them particularly if HEPH was merged with GIAI or a replacement was created,

Leading to the events of the multiplayer game, where Aloy might either seek to create an organisation that would be separate from all established tribes that could work together with GIAI or expand a pre-existing organisation such as the Hunters Lodge, where she Beta and their friends would be high ranking leaders,