Part targeting does sound difficult to balance. In fact, some ideas for part targeting have already been implemented to a degree. For example, Core Analyzer has a similar effect of targeting robot's core. However, the chance to proc this effect is low, and its effect cannot be stacked either. Additionally, the effect will only transfer 50% of the damage to the core, and some robots are immune to this effect so you can't use it against certain foes. As you can see, there are a lot of restrictions in place for this kind of part targeting. As a result, not a lot of players use them, even among experienced players.
Armor Integrity Analyzer has a reverse effect where you have higher chance to target any part except armor. Unlike the core analyzer, this one is highly praised. There is little restriction, and the only thing you have to worry about is the proc chance. However, such worry is obsolete when the exp. version has 90% chance to proc. For only one processor, your chance to target core or weapon parts will increase since their armor coverage will be out of the equation. (The only real restriction is that it only affects armored robots, not regular robots, but that's where part targeting really shines. It only matters if you're facing off against strong enemies)
Similarly, targeting important parts can be really powerful unless there are a lot of restrictions behind it. If the ability to target any part except armor is already so powerful, it would be even more powerful if you can target any one part of your own choice! The most important part would be weapons since they directly influence your survival. If you can get to destroy their weapons easily, the robots would be as good as dead. Targeting power, propulsion, or utility won't have similar effect like this and are probably not worth implementing. If weapon targeting is as restricted as core analyzer, would it be worth having it?