I have 2 ideas that kind of go together.
(1) In the options, you could select which weapons/devices are available for purchase. So if you wanted to make a small-missiles-only or no-shields game, you could.
(2) Have weapon modules or weapon packs that can be downloaded and plugged into the game. That way you could have a set of silly-weapons, a set of realistic-weapons, a set of futuristic-weapons, etc. Those who don't care for a certain category could go with the default ones. This would possibly allow people to create their own weapons?
1) The tech-level option gives _some_ control over this, though not fine control of individual weapons/devices.
2) Hmm, not sure how this would best be done, at the moment the weapons are pretty much hard-coded (some have special code, so it would require some kind of internal language to load them from separate files). The sillier (less conventional) they are the more special code they require.
Not sure how easy it would be to describe such a wide range of weapons with a simple language and whether it's currently worth the time needed to write a full language. Perhaps there's an existing language for this kind of thing. Maybe some time in the future.