All tank hull MGs that don’t currently work should. I don’t understand why it’s basically only M2A4 Stuart that has working hull mgs that are controllable also as commander (to my knowledge). Japan has some working hull mg’s but you must switch to machine gunner to use them. Simple and necessary solution is to make all tank hull MGs work and then allow them to be controlled by commander, maybe by a different control than normal so that hull mg isn’t firing when your turret is turned away firing at something else with co-axial, even though that’s not a huge issue- just a matter of ammo usage. I know this wouldn’t be hard. Just replace the placeholder MG’s that are there for some reason(that show up as “primary or secondary weapon” in x-ray) with the actual working ones…
Edit: On checking some other tanks in x-ray it seems than the machine gun has been repurposed as the smoke launcher, so that’s where your smokes are coming from. See chaffee or 75 sherman for examples, but there are certainly others.