Thor & Hulk
Asgard’s finest and the Green Gamma Goliath have not been mentioned in regards to Civil War except by their absence. they weren’t present in the comics either, but for vastly different reasons.
In the Comics, Thor was presumed dead after he had disappeared from Earth after preventing Ragnarok, and as part of their Pro-Registration Forces Reed Richards and Tony Stark had created a cyborg clone of Thor that could weird a recently recovered Mjolnir and believe itself to be the actual Thor. In the first major confrontation between pro and anti registration forces, the Thor-borg clone blasted Golaith (Bill Foster) through the chest killing him instantly, claiming the first casualty of the Civil War, seriously harming Tony’s cause and earning him the enmity of many of his former friends. This Thor clone was later trashed by the hero Hercules but it’s a side plot thankfully better left out of any movie.
With Hulk, getting him to choose a side in the first place might be the hard part but he’s too random an element to have in the mix. The property damage and loss of life from a clash between heroes involving the Hulk would all but prove the point that the Avengers need to be controlled. In the comics, Hulk was banished from Earth long before the Super Human Registration act thanks to a secret group of some of the most powerful heroes. As you can imagine that didn’t work out too well for anyone involved and you can check out the excellent collections Planet Hulk and World War Hulk to find out why.
As movie Thor left “Midgard” to investigate why so many infinity stones were turning up all of a sudden and the Hulk left the Avengers of his own accord, we’ll allegedly find out what the two of them have been up to in 2017’s Thor: Ragnorok