Two reasons, really - one is the aforementioned one dice less than a standard Ion Cannon attack. The second is that you actually need to hit with your primary weapon before you can fire it. I was considering making it range 1-2 as well, but thought that was a bit much.
I don't know; I'm still slightly favouring the systems version as it could potentially work with missiles as well - very thematic for the Gunboat - and the cannon version has synergy with the FCS.
Points values aside, both have flaws. I really don't thing the Gunboat should have access to the Mangler or HLC, but the cannon slot seems the easiest solution. It's perplexing.






