Just to be very radical for a moment, I think the Death Star should be unfinished. Perhaps more finished than in RotJ but still visibly still under construction.

That way the plans could be proof that the Empire is constructing a superweapon, rather than just being a technical readout which they hope will provide details of a weakness (though this was never guaranteed). Also it makes it more reasonable that the rebels would attack before it is completed, and more likely that they could scrape a victory.

I dont think it would be hard to change the views of the DS to look unfinished, it would just require the script to be checked for references to it being complete. It could still be operational with regards to being able to fire its main weapon.