A few notes;
Armour - Graf Spee's belt armour was 4" thick at maximum (most of it was thinner on all the ships), similar to the Leander class cruisers, Exeter's was slightly lighter at 3" max. In practice, the 11" shells ignored the cruisers armour, and the Germans were shocked to find that British shells pierced their armour, too.
Aircraft - a Fairey SeaFox from one of the RN ships (Ajax?) played an important role in spotting British fire but Graf Spee's Arado 196 was unflyable during the battle, having cracked its last spare engine cylinder the previous day. If it had carried out its normal dawn recce, it might have warned Captain Langsdorff of the true nature of his opponents (he initially misidentified the British ships as an obsolete WW1 light cruiser with two destroyers and confidently closed the range....whoops).
Gunnery - in general, maximum gun range considerably exceeded the distance at which hits could be scored. Visibility, the ability of fast - moving ships to dodge and rangefinding technology limited practical fire ranges to no more than 20,000 yards for any gun 6" and over (Graf Spee's 11" guns had a claimed maximum range of 37,000 yards).
Plunging fire - Complex one, this. Over a certain range for any gun, the shells start to arrive on the target at a very steep angle. Against ships, this results in a sudden drop off in accuracy - shallow angle fire causes a ship to cast a long 'shadow', so the error in range can be quite large (typically 200 -500 yards) and the shell still hits, against vertically plunging fire the range error must be less than the ship's own length.
Torpedoes - both sides fired torps during the battle, but did so at long range, and missed. Keeping the RN out of effective torpedo range was a major issue for Langsdorff, and torpedoing Graf Spee was the only realistic chance the British cruisers had of sinking her. (She was scuttled outside Montevideo because the Germans had been fooled into thinking the British had a battlecrusier waiting for her).
The design weakness that Commodore Harwood in Exeter exploited was that Graf Spee could only effectively engage one ship at a time with her main battery. Spee had two fire control directors, but splitting the turrets' fire would leave only three guns firing at each target, too few for an effective (ie accurate) salvo. The British ships played 'tag' with Spee, Exeter and the Leanders alternately closing to draw fire then pulling out of range.
Unlike sf space combat, where weapon effectiveness with range can be abstracted out, to my mind it's a rather important factor in WW2 war at sea.
To incorporate this in the game, I'd suggest that when one ship engages another with gunfire at over half her gun's maximum range, she first has to find the range, needing a '5' or better. This is reduced by two for each consecutive turn of shooting at the same target, so on the third turn, success is automatic. If the ship switches fire to a different target, the process must begin again. If the firer divides her shooting, the base score needed is a '6' reducing by one per turn.