In my original thoughts the Guardians did have a bigger role, at one point they were going to be the vessel that saved the Asgardians (and even Odin, though I eventually decided he had to die to show more of Thanos' ferocity as a villain) from Asgard, and the whole "chase in space" bit would have been curtailed.
The only reason the Guardians figured so prominently into the ML Infinity War, I think, was because of the Gamora/Thanos subplot. Since my version of Thanos is closer to the amoral psychopath of the comics, I felt that subplot was pointless, and thus there's less for the Guardians to do. I do show snippets of this plot, such as Thanos facing his greatest enemy in the daughter he lost in Soul World, but ultimately it isn't given near the weight it is in the film. Honestly my biggest criticism of Infinity War- Real Life Edition- is that it focuses TOO much on Thanos, when it should be more of a culmination of Phase 3 and its consequences. Since my version of events have more events than just the Civil War (the World War Hulk stuff, Tony as director of SHIELD, etc.), then that has to take precedence here.
Without giving too much away, while this is all a three-part story, the three parts could theoretically stand alone with a little reworking.