The GO:KEYS, even the latest GO:KEYS 5 stops well short of being a full-fledged arranger. I actually wrote Roland Support and appealed to them to add a control for "Sync Stop" or arranger "memory" in a future OS update. (Currently, once the style starts it can't be stopped by lifting from the keys.) They didn't add my requested functions in v1.10 but there's always hope.

YES! I would love to see the BK-9 rendered as software. You might have noticed that Ketron is offering a compact module called the EVM, with connections but almost no controls. From a study of its manual, it's basically the EventX module's software controlled from an external capacitive touch screen. I guess burning the program onto dedicated hardware is one way to control piracy or unauthorized distribution, but one could characterize the EVM as a "software arranger in a box." It's definitely more affordable than the EventX, and one could argue that a display and touch-screen interface, heck even a keybed aren't INHERENT to an arranger. Time will tell whether this approach catches on.