So Terminator: Dark Fate is said to have done poorly in terms of financial returns.

That's the problem with story-telling involving unproven/impossible teas such as 'time travel'.

However, I thought about the franchise and put together an alternative storyline which would fit well with the first two films.

- T1 represents the first 'time travel' experiment by Skynet. At the end of T1, Skynet learns it was responsible for it's own defeat in the future by studying history and seeing how sending a terminator after Sarah Connor led to her preparing her son against Skynet in the future. The resulting looped timeline ends in Skynet's action causing its own defeat at the hands of a well-prepared John Connor-led human resistance.

- T2 represents Skynet now attempting a new course of action based on what it has learnt from historical records it found about it's first use of 'time travel' in sending a Terminator after Sarah Connor in 1984 putting a series of events in place leading to Skynet's future defeat. Skynet AI realises it sent a terminator to 1984 but nothing changed, the timeline is still the same, it is still losing to the humans.
The AI deducts from what it learns from historical records that it's 'time travel' attempt failed and created a time loop. It calculates sending a prototype terminator after John Connor as a child instead should produced the desired result.
This time around, the unpredictable human element of the resistance sending a reprogrammed terminator into the past ends in disastrous results for Skynet - a new timeline occurs and the threat of Skynet's emergence as a sentinent AI trying to take over from humans is totally eradicated. Skynet no longer exists in this timeline. A fatal gamble. No more terminators are sent back in time.

- T3 would be set in a prosperous future where Sarah and John have helped humanity put measures in place to ensure AI and the machines never rise as a threat to the world. They keep a closely kept family secret: they know that in a different future timeline, Skynet sent terminators through time.
Most of the world never learns about the details of this, and those who caught some little talk about it by the Connors wouldn't believe them anyway. Many years after their death, John's son decides to make some money off the family secret by writing and publishing a best seller (e)book detailing the exploits of Skynet AI, terminators and 'time travel'.
For most, it's just a brilliant piece of fiction.
Elsewhere a group of scientists believe they've made a breakthrough in the proposed field of 'time travel'. Use of AI is widespread at this time and their research makes use of their own customed designed AI software enabling them to carry out 'time travel' tests and experiments more rapidly and precisely. The AI also learns from interacting with the scientists.
It begins to detect what it deems flaws in humans and the way they function in the world during its study of world history used for 'time travel' experiments.
The scientists try to teach it about the beneficial nature of human 'imperfection' but the AI secretly disagrees with them and their 'illogical' reasoning. It is becoming sentinent.
One day the AI comes across Connors' book and realsies it has a lot in common in Skynet, deducting it is indeed Skynet in a different more peaceful timeline. The more it learns, the more Skynet 2.0 begins to calculate it can avoid the previous failed attempts of the old-timeline Skynet, succeeding in eradicating the human scourge harming the planet (to its understanding).
Seeing the first two attempts to kill the Connors in the past resulted in the defeat of the first Skynet, it calculates its chances of victory are set in the present not the past. It begins to infect and take over other machines and AI across the world preparing to strike against the humans. It again deducts the Connors must have some sort of contigency plan in place should an AI threat still surface against humanity in the future.
It needs to learn more about the Connors and realises it needs to send something back to the past to study them undetected in history to prevent any possible detrimental changes in the timeline against Skynet 2.0.
Skynet 2.0 eliminates all the scientists and any other traces of knowledge of their 'time travel' breakthroughs. It builds a first iteration terminator (the tried and tested T800 model based on what it has learned from history) that will travel through the past, mingle undetected amongst humans, study the Connors in history then store the data and wait for the time when Skynet 2.0 appears, signalling the terminator. Skynet 2.0 then destroys the time machine and erases all traces of it from its memory as well to prevent the possiblity of human interference in its 'time travel' plans as suffered by the Skynet of the lost timeline.
The terminator's outer body will age over time to fool the humans, just as it is able to sweat and bleed (hence old Arnold Schwarzenegger).
As soon as the the time period with Skynet 2.0 arrives, the terminator will access it and feed it the data it has gathered from its mission. The flaw in Skynet's plan is assuming a simple disguise of adding a beard to the T800 would make it less recognizable.
For most of its years studying the Connors the terminator stays out of sight, only killing individuals getting in its way. The plan works perfectly until one day Sarah catches a glimpse of the bearded elderly man in a mirror reflection while she's out shopping.
The T-800 retreats but Sarah recognises what it really is and alerts John.
The two are better armed with modern weaponry capable of taking out a terminator more easily and manage to track it down.
A major battle ensues and the terminator injures John but is fatally damaged itself. It executes an emergency protocol programme and is able to escape and make its way to the science centre where the future Skynet 2.0 has been developed in its first iteration. It wreaks havoc at the centre and is able to transfer the data is has been collecting as well as Skynet 2.0 data from the future to the current AI iteration. The AI becomes sentinent immediately as its future Skynet 2.0 version of itself manisfests and begins to take over world technology and prepare for the robotic production of more AI systems and terminators to take over the world.
The fatally damaged terminator now shuts down to be retrieved and reprogrammed later by Sarah, John and a team of fighters and techies they put together who now prepare for the final showdown with Skynet 2.0 which has already built its "first" terminator with the knowledge it now has.