atm one has to do this in an expensive perFrame previous vs current check.
having an efficient EH would alllow also more systems as result.
params ["_unit","_weaponPrevious","_weaponNew"]; params ["_unit","_weaponPrevious","_weaponNew","_vehicle","_turret"];//for vehicles
Potentially also useful (not sure only previous or also both):
muzzle: String - muzzle mode: String - current mode of the weapon ammo: String - ammo
For MagazineChanged probably same setup useful with only weapon in addition