Bob, I don't know why you'd want to connect directly to the battery and lose all the benefits of the remote control, you'll have to explain that one. It's just as easy to simply connect the battery pack directly to the track feed and have the full functionality of the LC or LC+ locomotive.
Again, I'd opt for the higher voltage pack and run the electronics package the way it was designed, simple and effective. In one boxcar, you can haul enough batteries to run all day, so that's not really an issue.