In the hundreds and hundreds of SH1 patrols i went on comprised of dozens and dozens of carreers, i only ever sighted the Yamata once (sank her with 9 torpedoes and 1 Miss).
that is not to say she didn't steam by me a few times due to her high speed, and unfavorable heading and bearing when detected on sound or radar. but i only ever sighted her once.
i would rather see a random chance of .05% chance per mission of seeing the Royal Oak or the Bismark, than a scripted mission that is historically correct. But if a ship has been sunk during the War, it should not appear on that random encounter table.
this is why you would need a random encounter table for each patrol zone, for each time of day, for each weather pattern, for each month of the war. and the appropriate sub-tables to determine specific unit type.