From the ultimate goal, the New Army and Old Army are essentially the same: both aim to build a bridge.
Moreover, if we look purely at the ultimate goal of "reducing Void catastrophe," it doesn't seem to matter who succeeds between the New Army and Old Army: as long as the bridge is successfully built, the imbalance across the Void will drop below the critical value, and the Void catastrophe will occur in a relatively mild manner (although it will still be accompanied by numerous doomsdays, at least it won't cause mass extinction, and many worlds can be preserved), which is exactly why the New Empire decided to set aside past grudges with the Abyss Xyrin and work together to build the bridge.
