Ya, the nuts came loose on the impedance switch and the jack on mine. I just had to tighten them up. No big deal.
It never occurred to me to try slapping on my JC. It's just not the kind of bass I would take to a gig where I'm going to lay down some slap. I'd take my Stingray for that. Plus the JC is a passive bass, and I usually prefer to slap on an active bass. That's not to say it can't be done though. Lots of people have/do slap on passive basses.
In terms of the neck dimensions, I find it quite playable. The gloss finish on the back of the neck a bit sticky and I've been meaning to take the shine off with some steel wool but I haven't done that yet.
I'm not a good judge of neck profile because I've spent 30 years constantly switching up basses and playing different genres of music. I'd play whatever bass the gig calls for and I don't typically have much trouble adapting from one four string bass to another, as long as it's set up to my liking. I was able to set up the JC to my liking, and the tone is solid, so it's a keeper.
I read somewhere that the bass player from Death Cab For Cutie played a JC on the studio version of I Will Possess Your Heart. I don't know how much truth there is to that; it sounds like it could have been a p-bass to me. I find I can get a meaty p-bass style sound out of my JC, so the story is plausible. It's a real big aggressive sounding bass.
Here's the song, but like I said, I'm not sure if its true that he used a JC on this. He's shown in the video playing a vintage bass that is similar to an EB2 or a Rivoli (I'm not much of an expert on those hollow body basses). Who knows what he played on the recording.