The vehicles need a logic overhaul.

The Tank should have 2 shells, apfsds darts for anti tank and HE for anti building/ infantry. The darts will disable things (ex atv, humvee, boats) if it hits the engine and will kill a person if they are hit but, you have to be very precise. The sabot for them should be modeled and be a much less penetrating but still damaging shot. This type of shell goes between 1400 and 2000 m/s (above mach 5) and has very little drop with incredible accuracy. Because of the nature of darts, cannons on modern tanks are smoothbore which makes HE rounds less accurate. They are also full caliber and as such are slower and have a more pronounced drop, much like is currently modeled in game. This shell has lots of fragmentation and can kill anyone quite close to it.

Tanks should also have some level of armor. If you hit the upper front plate, it should do reduced damage for the first couple of shots as those will not penetrate. If you hit the lower, it should do full damage and the sides as well. The engine should be able to be disabled if a hit is scored from behind (this can be repaired with the repair gun, just like normal and a certain threshold will be set. This will decrease turret traverse, make movement impossible and if the tank is autoloaded, will increase loading time)

The SPAA (self propelled anti air, aka the anti air tank). SPAAs irl have "belts" for which ammo is loaded into the gun/guns (or auto cannons if you want to be specific). These can consist of, solid ap shot, he shot, apds, he-vt (a proximity fuse though not often in this low of a caliber as it highly restricts the already low explosive mass) or aphe. These shells are often cycled (for example, ap/apds then 2-3 he rounds then it resets for an anti aircraft belt or 2 ap/apds shells then an aphe/he shell for anti armor. This would allow for the SPAA to be more versatile in both anti-tank, anti-heli and anti-personnel. The SPAA should also not need more than 2 or three shots of 20mm he to kill a person and a single headshot should kill (these shells can have 5-30g of explosive mass which is plenty to one shot a person) and the heli damage should also be increased as you will not empty nearly 200 shells (of which at least 150 will hit) and not killing a heli.

The missiles that are currently on the SPAA are lock on, auto guided. This should be changed to be tow missiles. These are wire guided rockets which require skill to use and would allow you to take out humvees and tanks out past the operational range of the guns (which I like that yall made it to where you cant frontally kill the tank with the SPAA guns). They should use one of the buttons (along with all the other shell selections) to change between proxy (for aircraft) and heat (for tanks). They should be able to deal damage over the top of tanks and boats/atvs.

The helis need to switch between apds (to deal damage to tanks) and he (to deal with other aircraft and troops) in a belt (ex 2 apds then 2 HE). HE will do little damage to tanks and the Humvee but plenty to open top vehicles and aircraft.
Please, add interior controls. There should be the stick for roll and pitch with the right controller stick still for yaw and a lever for blade pitch angle (currently the job of the left stick forward and backwards)
They also need sensitivity settings as they are too sensitive for my liking.

The apache has currently molded, 2 rocket pods (with 8 rockets each I believe) and 8 hellfire missiles. I don't see need for the Hellfires. They could be a cool addition but without the addition of aps (active protection system) it would just be incredibly op and tanks would stand almost no chance. The rockets are seemingly based on the 70mm hydra rockets which have multiple warheads. This should be something you can change. They can have he rounds for most targets or heat for anti tank. He rounds will yield higher damage to everything except the Humvee and tank. HEAT will do little to troops