I think a similar case on the reprintings may have come up in the past. As a first pass, if it is apparent that they changed the packaging in some way, I think we may want a separate entry. However, if they are just resurrecting the old printing with another run, perhaps we should just use this entry. In that case, we may also need to investigate the idea of multiple print dates for albums that phase in and out of print over the years.
I'm not sure about Joe Hisaishi. I had hoped to dive in and put up the whole Yamato discography, but I just haven't had the time, and have a huge backlog of other submissions and code to write before I should do that. Those discs you mention contain music from the series and movie that came out in 1980, and this seems to predate his involvement in films, so it doesn't seem likely.
For what it's worth, I loved the music from the series, but I don't know if you should put that in the plus or minus column. :P