Well, Type 4s are hard to use, admittedly. They are not the most versatile either. Equipping them makes the battletransport-line unable to defend against gunboats. Equipping them on a 5k doesn't make any sense, because of the short range in relation to the ship's length.
It took me a long time to be able to use them effectively on medium transports. I never met anyone else who considered them effective against snubs in PvP. The problem is not hitting your target, but keeping the shields down to do any damage.
But then again, I never met anyone who liked the type 1s much. That's usually because of range and refire-rate.
This comes down to using type 2s and type 3s. If you see it that way there really is not much variety in usable transport-turrets.
What would help the type 4s popularity a great deal would simply be a better shield-damage ratio. That way it would be possible to use them efficiently against snubs, but they would still be no good against a gunboat.
Another possibility would be to introduce an EMP-missile turret for transports. This could even replace the current type 1 turret and would well be used in the same weapons group as an array of type 4 turrets.
' Wrote:for those who missed it: the moral of it all is ----> traders with teeth are fun for pirates. - within reason.