Here is some propositions for additional units to fill more roles in various armies where roles seem to be lacking somewhat.
Sdkfz 234/3 or Sdkfz 251/9 Stummel - Light vehicle armed with leIG 18 infantry gun (similar function to M8 Scott, mobile infantry fire support, HE-only, no turret)
StuH 42 - Direct fire support with 105mm gun, range approx. same as standard 75mm HE tank rounds (so not artillery). Function similar to M4 Sherman w/ 105mm. It is my opinion that guns like these, self-propelled, armoured large-caliber guns, are very good at countering artillery, since they can survive getting into range and pound it with heavy caliber (= pinning).
Sdkfz 251/D mit Wurfrahmen “Stuka Zu Fuss” - In Tech 3 w/ Tiger II, Jagdpanther, etc; has 6 x 300mm rockets, and is a self-propelled rocket launcher.
Sturmpanzer IV “Brummbar” - In Tech 2; similar to ISU-152, short-ranged 150mm direct-fire assault gun
M4 Halftrack - Standard halftrack with 80mm mortar (same as infantry). No MG, no resupply etc. For vehicle yard.
DUKW or LVT-4 - APCs capable of floating on water. DUKW is more like a truck, LVT-4 is a tracked, lightly-armoured vehicle.
M36 Jackson - Heavy tank destroyer with 90mm gun. US really lacks anti-armour capability on the ground.
M7 Priest - Self-propelled 105mm artillery.
SU-85 - For Tech 1; anti-armour capability, as they lack such in Tech 1 (ISU-152 is just not good at tank killing due to its low speed/maneuverability and enormous reloadtime). Turretless tank destroyer with 85mm gun (same as on T-34-85)
SU-100 - For Tech 2. 100mm anti-tank gun. The Soviet 85mm still will not be able to put up much of a fight against heavy tanks; they need something that can damage Tigers, Panthers and Tiger IIs, Churchills etc, as well as be able to destroy lighter armour from further distances. The IS-2 does not perform this function adequately; its gun isn’t that great against armour, it is slow, and has huge reload time.
SU-122 - Standard self-propelled 122mm artillery (M-30; Soviet medium artillery). Like Wespe and Sexton etc.
Wasp Carrier - Universal Carrier (small, jeep-like vehicle, except tracked) armed with flamethrower.
M4 Sherman Duplex Drive - Sherman with Duplex-Drive; allows it to float on water like a boat, basically.
Churchill Crocodile or AVRE - Crocodile was a Churchill with a large flamethrower instead of a gun; AVRE had a 340mm petard mortar; short range but could annihilate almost anything.
A lot of these units have potentially very powerful roles in countering artillery due to their armour and ability to lay down large-caliber fire. Self-propelled howitzers and assault guns IMO are very good at moving into range of enemy artillery in a hurry, without having to deploy or having a limited firearc, and laying down suppressive barrages. Unlike static artillery, they can withdraw immediately if threatened. I think this is a very underused aspect of gameplay and could help in large part to break artillery deadlocks; it just isn’t used much due to the low amount of actually available units for those roles.
Other units just provide functions that will be helpful in other areas. Yes, some may see “duplication” of roles between sides (Stummel performing the same role as the M8 Scott and Su-76), but they offer more tactical flexibility without adding a huge number of units. Just 3-4 per side (split between Vehicle Yards and Tank Yards). The Mortar halftrack for instance would be able to provide different types of support than the M8 Scott; it can fire over obstacles and will have a comparitively much larger ammunition storage. The Wasp is just cool shit, zipping around in a BA-64 type thing with a flamethrower. We could even give it a small transport capacity (~4 infantry) and it would become a very useful tool for running around with small squads on scouting missions, capping unprotected flags and causing mischief, just like they did in the real world.
They all have a role, y’see.