An idea I shared on the Terminator Wiki some time back and which I'm now bringing here to see what you guys think.
I understand this is a bit unusual, but then again these two franchises have some similarities; both stories take place in apocalyptic futures devastated by nuclear armageddon, both have advanced technology at their disposal, they both have their own "Judgement Days" and - with crossover stories like the Batman/Judge Dredd crossovers involving dimension jumping to different time periods - there are some good possibilities open here.
I could easily imagine Skynet been "rescued" by the Dark Judges (altering the events of T2; Judgement Day) and brought to Deadworld, with the two agreeing to join forces; Skynet wanting humanity dead because it views them as a threat to its own existence, while the Dark Judges want humanity dead because they've stated that being alive is a crime that is punishable by the death penalty - so their goals mostly align.
As such, the advanced technology of Deadworld is used to make legions of various Terminators, Hunter-Killers and even Spaceships. Honestly, I can imagine a scene on Deadworld looking like this but with Terminators and their technology/vehicles instead and the Dark Judges overlooking it all: https://www.youtube.com/watch?v=8buh5A70loA
Depending on how the story goes (and how the rules of time travel work for this event as Terminator crossovers tend to alternate between "Multiverse Theory" and "A Sound of Thunder" rules for time travel), you could potentially have the threat of a Multiversal War against the Machines - like a 2000AD version of the Doctor Who story "Supremacy of the Cybermen" as everyone comes under attack.
The way to resolve it completely, if it is "A Sound of Thunder" rules (like what happened in the Robocop vs. The Terminator crossover or the original ending for T2), might be an alternate version of T2: Judgement Day - with Dredd and Anderson using their dimension belts to travel to that timeline.
As such, they'd join the reprogrammed T-800 in protecting Sarah and John Connor from the T-1000, who in this story may be joined/possessed by Judge Death.
It's a wacky idea and would probably be non-canon, but then a lot of crossovers are. Besides, if Dredd can clash with the Xenomorphs, Predators and even the "Mars Attacks!" Aliens, why not the Terminators?
Curious to see what you guys think.