When you're doing something like this, pictures really make things clearer.
Since you don't intend to run on track power, just use a switch between the battery and the LC+ board. I don't use wire nuts, but they will work. I solder stuff as that's a connection I have confidence in. I've found too many wire nuts rattling around in engines sent to me for repair...
Don't forget adding the ability to charge the battery pack. Also, if you expect smoke and electrocouplers to work, you'll need two of these installed to get enough voltage for those functions.
