Currently we can define turrets where the "machine gun type weapon" (memoryPointGun[]={}) has multiple locations i.e. multiple visual guns. But its not possible animate them properly without having to script animations for each seperate gun (worse for performance) and it's not possible to let them fire synchronised (1 trigger pull = 1 shot from each gun).

1) Independant Gun animation
A more "simple" improvement on the animation side would be the addition of a "multigunreload" animationsource. It would act the same as the reload source, except its range is 0 to x, where x is the amount of guns in either the memoryPointGun array, or an independently specified amount of guns. Let's assume 4 visible guns, so source range would be 0.0 to 4.0. After shooting once, the source would go to 3.0 within reloadTime of the weapon class. After another shot it goes to 2.0 and so on. Once it reaches 0, it jumps back to 4.0 to complete the loop.
Alternatively one could use 0 to 1 as range but use "1/gun amount" change per shot - but that makes it arkward to work with for uneven numbers (e.g. 3 guns) due to rounding issues.

2) No synchronised firing possible
Would require changes to cfgweapons simulation. A "simultaneous shot property" in CfgWeapons, which instead of 1 projectile creates the amount specified per single shot in an instant could be added, which could solve this issue for the mentioned multi gun systems.
In addition, it could possibly also solve the highly fps dependant rate of fire for very fast firing guns - instead of trying to spawn bullets at a rate of 1000rpm, one could use 500rpm but create two shots at once. The performance draw from the projectiles would be the same, but the firing rate should be more consistent. Matched sounds and visuals would be able to mask this workaround for high rpm weapons.

Firing simultaneously is somewhat possible currently with a dirty workaround -> to set reloadTime near 0 (=infinite rpm) and set burst to whatever the amount of guns should fire at the same time. However, this requires that magazine capacitay equals amount of guns, meaning that as many magazines have to be added, as there are rounds per gun. Worse, the near infinite firing rate will be an issue when game fps is reduced, which will lead to arkward behaviour and look.

3) forced delay between weapon bursts
A "burst delay property" in CfgWeapons , which prevents a gun from shooting for the specified time after a burst (refering to the burst=<integer> property) is complete. This would allow to have fast firing weapons, but stop them from shooting too many bullets at once. Currently one must "abuse" the magazine capacity for such a thing- which can result in extreme amounts of magazines that have to be added and kept track of on vehicles, and allows no proper magazine reload.
A matching animationsource, reloadBurst or something like this, would be helpfull as well.

If point 2) is not feasible or too much work, this burst delay would also be an alternative in creating synchronised weapons. It would be an inferior solution (due to fps dependancy of the "near infinite rpm" weapon), but still better than current situation.

Use cases
Example 1) ZSU-57-2. It has two guns that fire simultaneous. This can be achieved with the workaround above, but then 150 magazines of 2 rounds each have to be added. Plus no real magazine reload delay is possible in this case. The real vehicle has a clip size of 4 per gun, after which it takes some time to reload the next clip. This is impossible to do with just the workaround.

Example 2) Finnish AMOS mortar system, 2-barreled mortar in one turret shooting selectively synchronised or in succession

Example 3) basically all air vehicles with multiple cannons/guns (WW2 and early Cold War planes, Helicopters with multiple Gunpods,...) - their rate of fire beeing capped to sub 1000 rpm means they have underwhelming representation in most cases. Some of this can be faked with the cfgweapon "multiplier" property and increased bullet damage workaround that is used for vanilla miniguns, but for planes with 4 and more guns it can't be masked like that anymore, it's too obvious. They would be the ones who would benefit most from a "simultaneous shot property" in cfg weapons.

Example 4) Naval gun turrets and Anti Air cannon/gun mounts (Bofors twin cannons, PomPom, ...)