If the BK-7m has the ability to send individual Parts out via MIDI (and mute them internally), and the ability to change what PC/00/32 codes those parts send, it could be the WS add-on that we all wish for...
Sadly, Roland have been stepping backwards on those capabilities for quite a while. I wouldn't rule out it being able to do this, but I wouldn't get my hopes up, either.
Without the ability to play what will probably be MUCH better sounds in something like a Kronos or MoXF, it is still essentially a Prelude or GW-8 in a box. Breaking OUT from that box is what could turn this into the piece of kit we all REALLY want...
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An arranger is just a tool. What matters is what you build with it..!