Re: Can planetary alignment be weaponized?
How advanced is this world? If the answer is very, then I may have a solution:
Say the world is protected by a massive shield system of some kind. Perhaps it doesn't have a molten core, so a massive magnetic shield is made instead in order to protect it from the solar wind. Perhaps the shield, in some extreme future sci-fi-ish way is capable of blocking the effects of massive gravity effects from nearby gas giants. Obviously, either is a massive undertaking, and your folks must be way into the talking computers and flying cars stages for it to work.
Well, perhaps things are pretty bad all the time, but once every so often when things line up the shield is particularly important. Maybe you end up directly between two gas giants once every so often, instead of passing them individually. Maybe its a binary system, with a smaller star orbiting a larger one, your planet a bit further out, and when the small star whips past real close things get dicey.
Your folks would be fitting happy under their shield. Normally, if it failed, it wouldn't be good for people. Maybe there'd be a few small earthquakes, or everyone would have to stay under cover from a barrage of radiation or whatever.
If it failed during one of the bad points, of course, things would be far worse. Perhaps mass destruction type worse.
All you need to do is make it so the shield system is split into different generators or whatever so that they can shut one down and get the area you want.
After that, the only real issue I can think of is why in hell people would live on a planet that needed such a ridiculous countermeasure to survive, as I'm assuming such a shield system would be somewhat expensive.