At the forefront of many of these designs were the concept artists, who, like the famed Ralph McQuarrie before them, were tasked with designing the reality of Rogue One.
The AT-ACT in Rogue One is clearly slightly different from the AT-ATs fans remember from The Empire Strikes Back, but the difference in the film is merely aesthetic.
New characters, ships, and locations are introduced in a way that very much fits into that era of Star Wars, smartly avoiding any violations of established continuity.
This concept art helps give an idea of how the cargo walkers are put to use on the Scarif base.