OK, got it working satisfatory, thanks to nominesine and others.
The problem was most likely that I executed the code before the ACM was initiated properly.
I wrote the code in the init line of the module, which didn't work as well as this solution:
init.sqf
if (isServer) then {[] execVM "laggy_acmScript.sqf"};
laggy_acmScript.sqf
waitUntil {!isNil {BIS_ACM getVariable "initDone"}};
waitUntil {BIS_ACM getVariable "initDone"};
[0.00001, BIS_ACM] call BIS_ACM_setIntensityFunc;
[["INS", "RU"], BIS_ACM] call BIS_ACM_setFactionsFunc;
This script keeps the script "paused" until I want the ACM to kick in.
To start the ACM, I have a trigger that is activated by a publicVariable, on activation:
[1, BIS_ACM] call BIS_ACM_setIntensityFunc;
Note that my ACM module is really named BIS_ACM in the editor.
This solution works well on a dedicated server to my experience and the intensity of fighting is OK.
Sometimes the mission is quite uneventful, even though the intensity is set to 1.
Therefore I wouldn't recommend setting the intensity lower than that.
Wish the intensity would be more consistent, but I guess that is the effect of randomness.
Laggy