I'll be happy to bare with you.
<takes off shirt>
Hey, don't do that! Before you know it, you'll be the one punching heads off. Those "no shirt" thoughts are pretty deadly!
Seriously, though, the only thing I know about ghost behavior is that they can reliably be trusted to hang around meeting areas most of the time; in my last Terrifying fort, the unmemorializable merchant dead used to be constantly haunting the memorial hall. You could probably set a meeting area aboveground to attract ghosts and hope they attacked goblins. The trouble is that this isn't guaranteed, and I wouldn't be surprised if ghosts looking for someone's head to crack will leave the meeting hall to do so. And "most of the time" isn't "all of the time". They just spent a lot of time there--it's a tendency, not a hard and fast rule.
The type of ghost is dependent on the dwarf's personality and mode of death. Some dwarves have worse tempers than others. I'm pretty sure that dwarves who died berserk or by murder are more likely to be violent ghosts, but that may just be because those dwarves are the ones with the bad tempers in the first place.
There's one way to weaponize ghosts that's indirect: Being "attacked by the dead" (NOT haunted; attacked) is a thought that goes toward the "doesn't care about anything anymore" descriptor. In a fort where dwarves were regularly attacked by weak violent ghosts, they could get that trait pretty fast. But zombies are much more reliable and safe for the purposes of "attacked by the dead", and seeing pets die is safer. I don't know if assigned wardogs count as pets, but if they do, that may be much preferable to keeping berserk baby ghosts around.