Yeah, always a pleasure to see you, SuperDeadite. I definitely feel that the SS version of LII is better on account of its extra scenarios. And the disparity in volume between the quiet streamed music and the raucous voices/sound effects in FX is really unfortunate. I hope you're enjoying GLVI; IMO, GLV took a turn for the worse in gameplay, which has made me hesitant to try GLVI.
Anyway, I got a pre-owned FX-BMP about 3 weeks ago and never touched it until today. I put some AAA batteries into the thing (of course it didn't come with any) and was surprised to see that all the save files from the previous owner are still there, completely contrary to the general assumption that no batteries = unusable FX-BMP. Now, this thing has been battery-less for at least a month, which is what piqued my curiosity.
Anyway, I have a strong suspicion it's a non-rechargeable battery in the FX-BMP since even brand new modules can save without the battery, whereas rechargeable batteries need to charge before any use. It's still only a fair guess at this point since the console, once connected/powered up, could be charging up a rechargeable battery in the FX-BMP for all I know.