So I had part of an idea- I notice that the plaque for the battery switch kind of calls attention to the fact that...it's the battery switch. So I picked up a spray can of that Plasti-Dip type stuff, and blacked it out. We still know what it is, how to use it, and how not to use it, but the casual car thief won't.
This stuff will peel off easily later if we want, without any damage to the plaque.
We're going to throw a padlock on the switch too (the black-colored Master 131 with the 5mm shank like mentioned earlier).
And for what it's worth, we tried the 141 with the 6mm shank, and it doesn't fit.