I was thinking about this film this morning while listening to the soundtrack of 'The Terminator' and feel like perhaps they shouldn't have created a new timeline from where they did, in this revised timeline, a T-800 series model 101 terminator was sent back to 1973 to protect the 9-year old Sarah Connor from a T-1000. And this is the start of a whole new sequence of events, which wipes out what happened in T1 and T2. I was wondering if they should have 'jumped in' after the events of T2, thereby retconning Rise of the Machines and Salvation.
What if the Resistance, instead of sending back Kyle Reese to 1984 sent back Pops, to go up against his Skynet-aligned doppelganger, both of them are the same series and model, so it could be a more interesting battle, with maybe only Sarah Connor's help would they be able to win. Then, instead of 'Uncle Bob' getting sent back to 1995, it is this time Kyle Reese who finds Sarah and Guardian being hunted by the Robert Patrick T-1000.
By the end of that story, Guardian could possibly sacrifice himself to destroy the T-1000 (like he was willing to do in Genisys against the T-3000) or after destroying the T-1000 willingly allow Sarah to lower him into the molten steel to prevent his future-technology being used to advance Skynet. Or maybe he does not die, he continues to protect Sarah and Kyle in 1995.
Assuming that Judgement Day would now occur in 2003 (Skynet developed by Cyber-Research Systems rather than Cyberdyne), they could try to stop that, or let it happen, because it might only be possible to postpone J-Day, Skynet will always in some form be created and the war begins. This new timeline could have 8-year old John Connor by then who is preparing for his future, or not depending if they tried to avert it or not.
I still wonder how Sarah and Guardian knew where to intercept the original terminator at the observatory, where and when, and similarly how the T-1000 knew where to find Kyle Reese shortly after his arrival in 1984, and subsequently by Sarah and Guardian.
I still wonder who sent Guardian back in the first place, we might never know, as far as I'm aware, there will be no sequel to Genisys. It feels like ever since T2, after James Cameron wasn't the director, the franchise has sort of been 'all over the place'. I think the rights revert to JC in 2019 so who knows, maybe he will do T3 following on from his story, and thereby ignore Rise of the Machines, Salvation and Genisys, oh and that awful TV series, the Sarah Connor Chronicles, not even easy to say that.
Final thought, on who sent Guardian back....a version of Skynet from the far-future in which machines have won and rule the world. It decides that it's existence is meaningless without an enemy to destroy, humanity is extinct, and the machines have no purpose, they just stop, with no clear objective. So it decides to erase itself from the timeline, and let humanity survive. Far fetched? slightly, but it would make a good twist, rather than Guardian being sent back by, I don't know, Doctor Emmett Brown maybe? 