I was planning on isolating the pack. Either take it out completely or if that was an issue, using some electrical tape/disc on both ends to isolate the batteries.

That plastic cap looks good too. My only concern would be because it’s outside the device, it may rise suspicion. Then what do I say? I did that so they don’t ignite? That should go over real well…

I never underestimate how much I need to underestimate some people.