Artillery projectile simulation:

Models of Artillery and Mortar shells are lackluster and either dont exist/dont show or look like imported from OFP.
In addition, there are big issues when trying to update, replace or make custom ones:
Ammo with simulation=shotShell displays models properly. But only if the initspeed is < 330m/s. Beyond that it simply wont show.
With simulation=shotBullet it displays the model irregardless of speed. However, it does not sync the models orientation with the bullet trajectory. The bullet will keep the orientation when it left the muzzle throughout its entire lifetime.

The trajectory of all artillery in Arma is wrong. It does not have airfriction, and as a result the ranges are considerably further and the time to impacts are shorter.
While i dont see this as big issue for vanilla, when somebody tries to implement airfriction, it will not be possible in a satisfying way.
The reason for this is that the "artillerycharge" feature in weapon firing modes only works when the ammo uses artilleryLock=1 property.
However, when the ammo uses said property, then the airfriction property will simply be ignored and assumed as 0.

As replacement for artillerycharge, the initspeed modifier for cfgweapons can be used. But for this to work one must use simulation=shotBullet. This effectively removes the possibility to implement a visual model for the projectile (unless it's a 17th century cannoball), and also removes any recoil force and other shell specific simulationfeatures.

Suggested actions:
Remove the automatic hiding of models from shotShell projectiles. If a model is not supposed to be show for specific weapons, dont define a model (or an empty model), simple as that.
Implement the speed-modifier feature that is working for shotBullet to shotShell for well. Alternatively remove the depenceny of artillerycharge in CfgWeapon from artilleryLock=1 property in CfgAmmo.
Other features that shotBullet received with the last DLC's should be added to shotShell as well (seperate ticket here https://feedback.bistudio.com/T121475). Alternatively, remove shotShell/make it a copy of shotBullet and add the differences in simulation as configurable parameters.

Artillery Gameplay:
The artillerycomputer is in most cases overpowered and also very uninteresting. It should be improved to make it more engaging for the player and also more usefull.
In addition it only calculates indirect (angle >45°) solutions and is therefore very limited.

1. Currently it can only calculate indirect solutions (angle>45°). Implement a toggle for the player to calculate direct solutions instead. Both are usefull in different situations. If the player wants to play optimally, he has to choose the best fitting solution type. Indirect mode can remain default, as it works in most cases. related: https://feedback.bistudio.com/T85404
2. When firing via the howitzer optic, it is almost impossible currently to fire at closer ranges, as only indirect solutions are available. Either also implement a direct mode for the "optical FCS", or provide a method to show a secondary optic that follows the gun elevation like for a normal tank gun for example.
3. Change the functionality of the artillerycomputer. It should calculate the firing data (direction and elevation) for you. But the gun laying should have to be done manually by the player. It gives them something to do and adds deviations from the player to the "perfect" solution.
4. Currently when using the artillerycomputer, the barrel and turret snap to the computed direction and elevation almost instantly / ludicrously fast. When 2) is not implemented then this should be fixed regardless.
5. UI elevation and direction indicators in the optic for artillery do not compensate for any slope angle of the terrain the vehicle stands on. Both, compensated and uncompensated angle should be shown. One for firing accurately, the other for seeing the limits/orientation in relation to the vehicle.
6. Change damage of artillery (ticket here https://feedback.bistudio.com/T116969). Its unrealistically strong in the current state, and the reason why many servers prohibit it.
7. Modability - It would be beneficial to be able to add custom behaviour for the artillery computer. Currently it seems totally inaccessable.