I don't think so the easy way.
But ofcourse you can work around it. I'd create a trigger around the vehicle [Present, Repeatedly], activated by [enemy side].
Condition: this and alive YourVehicleName
Activation: EnemiesHere = thislist; [YourVehicleName] exec "FireAtVehicle.sqs".
____
Then in FireAtVehicle.sqs you'd order them DoTarget and DoFire at the position of the Vehicle. Something like this:
;little script to target at empty vehicle...not tested ;)
;syntax: [YourVehicleName] exec "FireAtVehicle.sqs", where YourVehicleName is the target.
_i =0
_Target = _this select 0
#loop
~0.01
?!(alive _target): exit
_dude = EnemiesHere select _i
;distance check, so they have to be within 25 meters before firing (change this as you like
_dis = _dude distance _target
?_dis > 25 goto "SkipTargetting"
_dude DoTarget _target
~0.5
_dude Dofire _target
#SkipTargetting
_I =_i +1
?_i > (count EnemiesHere): _i = 0
goto "loop"