I think the problem with setting the rotation to off is that there is zero leeway - the target has to be exactly lined up !
You could (and I am not sure if this is a good idea) limit the amount of rotation to just a few degrees - by forcing the turret to turn back to stay inside limits.
Here is the turret demo hacked around a little. Hopefully in a future update there could be a little more flexibility in the (fixed rotation ) aiming ?
Turret Hack