Well, it's all up to Dioxine any ways.. (Or up to yourself if you decide to mod Piratez)
I think putting light weapons in heavy slots makes sense. They're kind of similar in that they shoot projectiles, just that the heavy ones are bigger guns with bigger projectiles. I agree that missiles should remain restricted to missile slots, and heavy to heavy slots. It's not about making every craft able to use every weapon. It's about making crafts with heavy slots more useful. If a cruiser (vanilla battleship) can use plasma spitters (light weapon), pirate heavy crafts should be able to as well!
As for buff items, that's partially why I was talking about defining new weapon types for them: Then you can pick where they can go. Currently they are considered weapons instead, which is a bit odd.
The light "buff weapon" is shields, which actually could be very useful on tank crafts (say limited to 2 per craft or something). I personally think shields and targetters should be able to be equipped on any slot, and keep thrusters for missile slots.
That way interceptors can be build either:
- dodgy machine gun interceptor (as currently, 2 light + 2 thrusters) perfect for chancing light combat crafts
- accurate machine gun one (as currently, 2 light + 2 targetters) for freighters and the likes (but heavier gunships could be better at that)
but also:
- accurate missile one (2 targetters + 2 missiles) great for supporting a tank and taking down military crafts.
- shield + machine guns for non shielded crafts with light weapons
whereas shield + missiles is rather useless: You want missiles because they are better against shields, but shielded things hit much too hard for regular interceptors to be good tanks unless they rely on dodge, regardless of shield add-ons.
And then, if you have enough support crafts, you can build a shielded tank to try to lower the damage taken/repair time. Although if you have good guns it might be better to use those to kill the target faster instead.
I feel like opening up lights for heavy makes heavy crafts more interesting (want to field interceptors with 2x light + 2x targetters or gunships with 3x lights or heavy? The former is better against small UFOs, the latter against big ones) and freeing some of the buff items means even more variety of builds for interceptors (ex.: an accurate missile ship is not a good choice for intercepting lighter UFOs, but is great support for military ones, so then you want also a good light UFO interceptor, and maybe a good supply ship interceptor too, which isn't the same).