Corrected entry: When Jyn and Cassian retrieve the death star plans they decide to use their shuttle to deliver the plans to the rebels. They scrap that plan once they realise that the planetary shield is up, which would block their escape. So they decide to transmit the plans digitally. But the shield would block their transmission so they get the rebels to blow it up. If either of their plans required the destruction of the shield then they should have used their shuttle to transport the plans. Then they probably would have survived the destruction of the planet.
Correction: From what I understand, the plan was never to use the shuttle to transmit the data. They needed to link the shuttle to the tower so that they could inform the fleet that the shield needed to be taken down in order to upload the data from the planet. Once the message was sent, the shuttle was destroyed by a grenade, and the two Star Destroyers were pushed into the shield gate to make the upload possible.
Correction: You are assuming that they knew at the time the decision is made that they know the Death Star will fire on the planet. Also they are in the building with the transmitter, to fly away they would have to survive getting to a shuttle and the flight in the shuttle with a lot of fighting going on around them.
I agree with your points here, but I do think it's odd that none of this is articulated or even alluded to in the movie. They basically say they can't do plan A because the shield will be up, so they move on to plan B. But then they say, well to do plan B, we need to get the shield down. No mention of anything like "well, either way we need to get the shield down." Not necessarily a mistake, but just odd.