[God Emperor]

I've got a feeling that your idea can be done actually. In the Components file, Point Defence has Ftr\Sat\Seekers as Weapons target and Point Defence as an ability.
As a test, I suggest that you modify the Weapon target to include "\Ship" and see whether your weapons activate. If it does work, it should be pretty easy to create a new weapon type which is "Ship" only - Interdiction Beam?

Sounds like an interesting idea to me and will be interested to hear your results. If your test goes well and you are not sure what to do, I could create a mod this weekend coming (long weekend for us West Australians)if you like (busy at work currently)...