An expanded idea from another thread.

In order to improve continuity between RO and ANH, show Vader’s shuttle docking with the flagship and the Rebels running through the halls in desperation, carrying the floppy disk. Perhaps they think that they can get away with it in an escape pod (like in ANH), but when the door jams and Vader appears, they quickly hand the plans to an officer on the other side of the door, who plugs it back into the ship (using the shot of him removing the plans except reversed), and transmits the plans from that station to the Tantive, which is waiting at the edge of the system.

As the door is forcibly sliced open and the rest of the soldiers perish, cut to the Tantive IV flying through empty space (VFX work would be needed to remove the flagship and the planet below). The movie ends as it does originally, sans Scarif.