Spinal weapons (e.g. nukes, railguns) set to hold fire often fail to shoot when spun or rapidly fanned, even when they have a target set and should be able to fire. I've heard that the reason for this is because of the game's tick rate - rapidly moving weapons will go from facing too far one way to facing too far the other way, without ever being in between.
One solution to this could be to let a weapon have multiple active targets. Right now a player can queue multiple targets for a gun, but AFAIK it only considers one of those targets of a time. If it would check each of the targets in order (firing at the first one with LoS), that might let players use rapidly moving spinal weapons without having to autofire.
Other possible solutions include - allowing players to target an area instead of a specific part, or allowing spinal weapons to shoot at a target even if they can't quite hit it.