what would YOU have done for T6?
and you still got same team of Arnold, Linda, Furlong, Cameron producing, Tim Miller directing. but you can change/rework the 'Dark Fate' story.
Imo:
a return to the lower budget hard R/18 rated dark horror noir of T1 (budget 100m, less CG more practical stuff makeup/animatronics/real explosions/blood squibs, set at night in LA whole film over course of few hours - also inspiration from those nasty late 80s/early 90s Terminator comics). that feel of a doomed world only few people know about..
No trilogy starter either just a self contained story maybe even a wrap of the saga.
Opening credits: (Brad Fidel scoring) T1 style block capitals interspersed with recreation of 2029 blue night battles. Exactly like T1/2. We see fleeting glimpses of the end of war/time chamber/terminators being sent back (CG 1984 Arnold/Biehn, 1991 Arnold/RPatrick) - basically the fan pleasing blue night purple plasma future war T3 movie that cameron should've directed in the late 90s but instead of a whole movie or opening 20minutes its just a minute or so spread throughout the opening credits like Superman II (and maybe Cameron could've taken time out of his Avatar sequels to direct the future war segment like he did the T2-3D ride)
Plot: present day. CG 1984 Arnold T800 comes back to kill john conner (like the opening to T:DF but the whole movie).no protector/grace or Rev9. at some point Sarah Conner turns up saves john and they try figure out wtf is going on and how another T800 has been sent back. they track down Miles Dysons son Danny who tells them he had continued his dads work at 'new cyberdyne' (called something else) and set about developing AI based on old backed up research from Cyberdyne (he since resigned but the work continued) and that a few years ago a man who claimed he was from the future had been caught trying to blow up the company building ...they find out the man had been put in a mental hospital (like sarah was) so they head there for more info/break him out. the man turns out to be...Kyle Reese! (Michael Biehn). he explains he had been sent back from further in the future (2050s) in a last ditch effort to prevent a far worse fate than T1/T2 from happening where another AI ('Legion') will end up taking control of the entire planet and killing everyone (no resistance winning the war - all they were able to do was send back Reese to try prevent it like Bruce Willis in 12 Monkeys).. reese feels some kind of connection to sarah but cant be sure why .. then the T800 tracks them and kills Reese as Danny is killed by SWAT (just like his old man lol) there follows relentless gritty night-time brutal action scenes as John/Sarah fight the Terminator (as in T1 the T800 is an absolute mofo to kill. no bullet in chest BS like TG).
sarah and john make their way to 'nu cyberdyne' to try and do what Reese failed to. but the T800 tracks them. eventually they disable the T800 but in doing so sarah is fatally wounded (like Reese at the end of T1). they retrieve the T800s cpu and are able to 'play' its memory and they find out that this 3rd terminator had killed john in 2029 (john watches the terminator footage of his own death) and that skynet sent it back before the time machine was destroyed. then theres the big twist where they finally uncover the T1 time loop (Sarah, Kyle, John, skynet, the terminators) and realise skynet/judgement day/the rise of the machines is inevitable and should have happened/has to happen. and that if its prevented (like they tried in T2) chaos endures and splinter realities happen (like T345) leading to the eventual far worse 'Legion' fate which results in humanity wiped out. so its either the Skynet future or the far worse Legion future.
as sarah dies from her injuries as she tells john to reset the future in order for the original T1 time loop to take place and close itself - which means allowing 'nu cyberdyne' to resume its work on the T800 cpu which would bring about judgement day (probably in the next few days/weeks as soon as the cpu is discovered and plugged in).
final scene ends with john in truck/jeep (the photo of his mother on the dashboard) travelling to mexico to gear up for the inevitable battle that lays ahead..
so I guess its not only a complete reworking of DF adapting some stuff (Legion, T800 killing John) its kind of a reworking of T1 (evil Arnie, same night-time dark horror noir feel) T2 (mental hospital, Dyson, cyberdyne building, ultimately undoing what they did in that movie, plus the reverse of Good T800 v Sarah/John) with T3 (judgement day is inevitable end, T800 killing John in the future), T4 (uncertainty regarding the future) and even some Genisys lol (alternate realities/the ending in 'nu Cyberdyne')
something like this trailer https://www.youtube.com/watch?v=SdnMTM5_6Cg