I don't know that they made improvements, but my VL-BB also doesn't have a battery option. They use the same sound board as other locomotives with a battery, so one presumes that with the correct cable you could add a battery. Fitting it into the VL-BB locomotive would be a challenge. FWIW, the board used supports a battery, here's the one in the VL-BB tender and locomotive, note that both still have the battery provision.
My solution will be to use this when I get around to putting batteries in, I know the guy that makes them.