You can't remap anything in the SD 2, because you can't STORE anything in the SD 2 at all. It will be a wild goose chase to try to call up SD 2 sounds by having the BK-9 send its own internal PC midi commands. You won't be able to address the high-quality sounds outside the GM bank. As I wrote you need to send specific controllable PC/MSB/LSB commands to the SD2 for each song you play, which you can do with master functions such as the MOX or Motif has, with the iPAD app Set List Maker or by preparing midi files in this way.
I have been thinking about buying an SD 1000 myself, this is why I inquired about it.