Krennic should have shot Jyn at the top of the tower just before she could pull the lever to transmit the plans. Tarkin should have blasted the horizon just to explicitly fuck with Krennic while taking the Death Star for himself once and for all. Seeing that the Empire had finally fucked him over as well after listening to Jyn's speech about the Empire being assholes, Krennic should have pulled the lever and transmitted the plans moments before death.
This would have made all of Jyn's speeches actually have something to do with the plot, and created a theme of the Rebellion being an idea that jumps from person to person. It also would have made the Empire's ultimate downfall the clear result of Tarkin's hubris.