I tried (and that works) to randomize units in spawning group, number and type. CUP units are from configVehicle with CUP vehicle addon:
_redmen = ["CUP_O_TK_Soldier","CUP_O_TK_Soldier_AR","CUP_O_TK_Soldier_GL","CUP_O_TK_Soldier_AMG","CUP_O_TK_Soldier_MG","CUP_O_TK_Soldier_HAT","CUP_O_TK_Medic"];
_redprepare = ["CUP_O_TK_Commander","CUP_O_TK_Officer"];
_nbr = (floor random 7) max 2;
for "_i" from 1 to _nbr do {
_redprepare pushback (_redmen select floor random 7)};
_redteam = [_pos, east, _redprepare, [], [], [], [], [], 0] call BIS_fnc_spawnGroup;