If you had hidden deployments and hold units off the board if they cannot be sighted by the enemy that will go a long way in creating the realistic FOG and hesitancy commanders and crews were faced with.
One factor which IMO is rather under-represented in many war-games is the morale effect produced by surprise, panic, sudden and unexpected flank/rear attacks, even fire from an unexpected source or direction.
Leaving aside the matter of special negative modifiers for surprise, flank and rear threats, etc, I can testify from personal experience that hidden units and hidden movement all by themselves can DRAMATICALLY alter game-play
I agree with all these statements. I've been running German Southwest Africa colonial games for over 15 years. The feedback I consistently get from my players is that including these challenging historically-derived elements – especially hidden deployment and movement – adds to, rather than subtracts from, their enjoyment of the game. As one player enthusiastically described it: "this was the most fun headache I ever had!"
Because of their use of smokeless powder and their expert use of cover, concealed Herero riflemen could continuously and furiously shoot at the Germans without being spotted:
(1) A description of concealed Hereros shooting at the Germans from boulder fighting positions:
"Although the 5th Company during its advance had been continuously and vigorously fired upon by the enemy, it could see nothing of them, so well had the smokeless-powder firing Hereros concealed themselves in the rocky and cover-rich terrain." (Translation by Roy Jones)
"Obwohl die 5. Kompagnie während ihres Vorgehens dauernd lebhaft vom Feinde beschossen worden war, konnte sie nichts von diesem sehen, so gut hatten die mit rauchschwachem Pulver schießenden Hereros sich in dem felsigen und deckungsreichen Gelände versteckt." (Generalstab, pg. 85)
(2) A description of concealed Hereros shooting at the Germans from dense thorn bushes:
"One did not see the [enemy] at all; from this morning on I lie in the skirmishing line; I have seen bushes and trees, and I have roasted in the sun; bullets have whistled around me the entire day, but I have not set eyes upon a single Herero." (Translation by Roy Jones)
"Die schwarzen Satanskerle sieht man ja nicht; von heute früh an liege ich in der Schützenlinie, Büsche und Bäume habe ich gesehen, und gebraten habe ich in der Sonne, die Kugeln haben den ganzen Tag um mich herumgepfiffen, aber einen Herero habe ich nicht zu Gesicht bekommen." (Bayer, pg. 61)
(3) A description of concealed Hereros shooting at the Germans, and yet remaining undetectable by eagle-eyed Native Infantry or German field glasses:
"…now however [enemy fire] also began to arise on the right, [from] across the river. I therefore threw myself into the skirmishing line of the Bastards…and observed the bushes on the opposite bank with field glasses. Yet I saw nothing of the enemy, and even the Bastard soldiers, with their sharp eyes that were accustomed to these surroundings, could detect none of the enemy riflemen." (Translation by Roy Jones)
"…nun begann es sich aber auch rechts über dem Rivier zu regen. Ich warf mich daher in die Schützenlinie der Bastards…und beobachtete mit dem Glase die Büsche am jenseitigen Ufer. Doch sah ich nichts vom Gegner, und selbst die Bastardsoldaten mit ihren an diese Umgebung gewöhnten, scharfen Augen konnten keinen der feindlichen Schützen entdecken." (Bayer, pp. 57-58)
(4) A description of concealed Hereros shooting at the Germans from close range, and yet remaining undetectable:
"But the enemy had so excellently concealed themselves behind the bushes or in the grass, that they were as good as invisible and one could inflict no damage against them with gunfire, although they were less than 100 m distant. From the outset several members of the machinegun crew were killed." (Translation by Roy Jones)
"Aber der Feind hatte sich hinter den Büschen oder im Grase so vorzüglich versteckt, daß er so gut wie unsichtbar war und man ihm mit Feueur keinen Schaden zufügen kontte, obwohl er weniger als 100 m entfernt war. Von der Bedienungsmannschaft des Maschinengewehres fielen gleich anfangs mehrere Leute." (Generalstab, pg. 67)
("Generalstab" refers to the German General Staff official history of the Herero War, and "Bayer" to Maximilian Bayer's first-person account of several of the battles.)
Thus, in my games, concealed Herero units are not put out on the board. As was the case historically, the Hereros remain concealed even after they begin firing. Thus, a concealed Herero unit that shoots is still NOT put out on the board – and its location still remains unrevealed to the Germans.
The German players initially confront an apparently empty battlefield. Even as the Germans take fire from the Hereros and suffer casualties, they still see nothing.
The German players must therefore maneuver, while under Herero fire, until they get close enough to spot the concealed Hereros. The Germans can use their rifles, machine guns, and artillery to suppress some suspected Herero positions, thus forcing concealed Herero riflemen to keep their heads down. This reduces the volume of fire the Hereros can deliver against German troops, allowing the Germans to advance.
However, suppression causes no Herero casualties. Against concealed Hereros, the lethal impact even of artillery was described by the Germans historically as "extremely negligible", "only negligible", "not especially effective" and "completely failed" ("äußerst gering", "nur gering", "ohne besondere Wirkung" and "völlig ausfiel").
So, for the Germans to inflict damage on the Hereros and cause casualties (whether by gunfire or by the bayonet), the Germans need to intelligently maneuver and get close enough to their invisible foe so that they can spot them and thus target them.
My players describe this experience of operating with such limited intel about the enemy's deployment as challenging, sometimes frustrating, but also quite exciting. One player described the German Southwest Africa games as "inevitably, the most fun and the most frustrating games" he plays at the HMGS conventions.
The Germans were not the only ones who operated with limited intel. Both the Germans and the Hereros were sometimes unexpectedly shot at or charged from the flank or even the rear. So, both the German and Herero players are subject to receiving fire from unseen, off-board units on their flanks or rear, or to being suddenly attacked in the flank or the rear by an enemy unit charging from off-board.
I've seen many a Herero player think they had the battle all sewn up, and that they were in an unassailable position to defeat and destroy the Germans located in front of them. Heck, the Hereros who fought at that same battle historically probably thought the same thing. But then, as was the case historically, the Hereros are unexpectedly charged from the rear. And then, the chaos and panic ensues, as the Hereros are forced to abandon what they thought was an unassailable position, or call off what was going to be a crushing attack, because otherwise they face the possibility of being enveloped by the Germans to their front and by the new German threat in their rear.
So, hidden deployment and movement, and off-board shooting and off-board charging from the flank or the rear, can make for a game that is fun, challenging, and historically derived.