I am more interested in dust and smoke for spotting, that would be an interesting feature (thinking in particular desert).
Actually, artificial smoke played a vital role in WW2:
In the German Army, smoke rounds were available for almost every artillery piece, including mortars.
Prior to an attack, if arty was available, and if the CO deemed it to be useful, arty would drop smoke rounds to cover an infantry assault. But even down on platoon level, soldiers would drop smoke to disengage or to drop smoke on open fields, prior to an attack, if it was useful/available.
German tanks had smoke dischargers ("Nebelbecher" = fog cups, means smoke cups) mounted on the sides of their turrets, basically pipes loaded with smoke rounds that would be dropped at a distance (electric ignition):
The first series of Tiger I production models had received these cups, but the main purpose was to launch S-Mines, HE-mines or charges filled with up to 360 metal balls (steel early in the war, steel scrap metal and then even steel cores from AP infantry ammunition [standard rifle AP rounds] at later stages of the war) packed into the outer ring of the case, and with TNT in the larger inner case, to counter close-in infantry attacks, intially, since the Tiger designers envisioned the tank to be a breakthrough tank. Since the Tiger's low speed and finicky clutch and transmission/gearbox didn't really allow for rushing enemy lines, and since the Tigers were then gathered in heavy tank Bns for Schwerpunkt deployments and often used as firebrigade assets, the cups were used for smoke rounds eventually.
Panzer IV's received these smoke cups, as well.
Because there were incidents where the smoke rounds got set on fire by enemy small arms fire, where the fire/smoke then sometimes incapacitated crew members, the Germans started to remove the external cups and introduced the "Nahverteidigungswaffe" (might translate to "close-in defense weapon") in the Panther and the Tiger II, which enabled the crew to fire smoke rounds from under the armor. It was basically a shaft under the armor -with an angle/elevation of around 40 or 45 degrees - protected by a hatch on the armor's roof, connecting to the outside part of the cup/"barrel", when the hatch was opened. The shaft was specifically designed for the smoke round's calibre. The crew could also remove the plug, means the launch mechanism/ignition plug and they could then use the open port to fire over-calibre rounds for the Kampfpistole, which was pretty much like the standard issue German Army flare gun (same calibre, pretty much the same design), but which was used to fire several types of HE ammunition (HE or HE frag rounds).
Demonstration of the Kampfpistole in Russia, 1943:
Some same-calibre ammunition even had fin stabilizers that made the projectiles look like little bombs (projectile number 3 is the same as number 4, just without cartridge for the propellant) :
http://www.custermen.net/nahvert/nah.htm
(Some info on that site has factual errors, overall it's a good explanation, though. For instance, the same-calibre rounds for the Kampfpistole that are rifled, are not rifled to "fit in the pistol's barrel", but because the accuracy of the pistol was so low - 4 meters spread at a distance of 70 meters, already -, so that the rifling must have been added in an attempt to improve either accuracy or range - or both)
The US Army picked up the idea of having smoke dischargers from the Germans and started to introduce external smoke cups in early 1944, it seems, at least officially (according to the Chief of Ordnance brochure "M4 Sherman Tank modification and upgrades from
Army Motors, Maintenance Branch, Office of Chief of Ordnance, Vol. 5, No. 1, April 1944"):
The Brochure explicitly mentions "smoke bomb throwers" as new feature for the M4 (left side, list of features pointing at the turret):
It seems like the Brits had adopted it, too (but when?).
Whatsoever, it's hard to come across footage where you can actually see US Shermans with Smoke Cups on the European theater.
Interestingly, the following picture shows the 2nd Polish Armored Division in Italy, and the tank in the front has smoke cups (bottom right corner). Most of the other tanks don't have cups , I can see one other tank (if I zoom in, in the second row, the 4th tank in the row with the gap), only, so I am guessing that these new modifications were not widely available, at the time, and that the application did not see widespread use until really late in the war:
That said, some nations/units/tank types had smoke rounds available, which enabled a given tank unit to disengage - under smoke cover - within minutes. Disengaging appears to be really hard in the game, across the board, no matter if it's a wheeled unit or a foot unit.
Historically, and technically, a tank unit had the possibility to pop smoke. And if say US tanks didn't have the feature, they would open their hatches and just drop smoke canisters/grenades. In city fights in Germany, if tanks could not get past German bunkers, AT emplacements or AT inf, GIs would pop smoke for their tankers, if necessary, to cover the retreat. Allied and German artillery (mostly mortars on the US side, but also common with German mortar units) would also pop smoke, either in front of the friendly units, or on top of the enemy, to "blind" attacking German tanks for a short period.
Smoke was not just used to prepare assaults.