> I've been very careful to fuse everything as you suggest, but my bus bars are exposed.

Wrap as much of them in heatshrink tube as you can, that should be the easiest.

> Do I want my cancer radiation treatments or flight software to go through rigorous checks? Absolutely. Does my web store need the same kind of rigour? Probably not.

Hmmyeah, but getting your web store breached can still have serious financial implications.