I've had a detailed look at mine this morning.
I reckon it is possible to remove the door card with the door closed.
The seals are close, but don't actually touch the flange around the edges, so there's nothing to stop the door card pulling free from the door.
The screw (it's a No2 Pozidrive) on the rearward end of the door pocket will need a particularly length screwdriver, as it's quite close to the plastic trim, but other than that, all fixings are easily got at from inside. Removing the rear seats might give you more room, but also means there's nothing comfortable to sit on while working on it.