In my opinion, it would be preferable to make the behavior of the missile similar to that of the cannon shells, but it seems to me that two shells which this cross explodes which would limit their use ...
In the second case, this would mean creating a wall (s) resistant to all types of damage, which risks making the construction of the defenses laborious and exposing the robots unnecessarily.
A third solution would be to immunize the defenses to turret damage but not knowing the method used to manage this. I don't know if it can be done.
It could be interesting to create a lot of area around the turret in which it will rock and destroy it in the event that it is crossed for the second time.
... but that risks exploding the rocket from the launch in the event of malfunction
So for my reflection what do you think?