It strikes me that there might eventually be an issue with Butters and Bob playing Batman, and that's the Council.
Remember, Luccio told Harry that they knew about Bob, as a former assistant-spirit to Kemmler. She also said that the Council had a 'destroy on site' order out for Bob, because he was too dangerous to be allowed to run loose, and in fact that he had been destroyed. In fact, of course, Justin had taken the skull from Kemmler's base and Harry had inherited him.
But now Butters is out there using Bob to energize various magical weapons and tools, and using them relatively openly. If the Council notices that Butters is suddenly wielding devices using way more magical energy than he should be able to manifest, someone might get curious as to how the former medical examiner is suddenly tapped into so much power, and if they took a closer look and realized how he was doing it, then suddenly Harry and Butters and the Chicago Alliance have Trouble with a capitol T right here Lake Michigan City.
I wonder if anybody's thought about that risk...