Great thread.
Back when I first started doing one-man-band stuff, before arrangers, organs had only a handful of styles. A 4/4, a 3/4 a March, a Bossanova, later a 6/8. Early arrangers weren't a lot better. I used an external drum machine for the first few generations of arrangers, up to Technics KN2000.
It was fairly easy to build a basic style to sync with the drum machine. All you needed was bass line, guitar strum and piano chord. Quantize feature made it easier.
I did ALL the songs with maybe six or eight styles.
Thank goodness the technology is way better now. I still tend to use my favorite generic styles a lot, but they still have not much more than bass lines, guitar strums, piano, a little organ or vocal bed on some. I don't like sustained strings on the style or left hand, as a rule.
The occasional Song style is nice, but as mentioned, pretty much limited to the one song.
It is great that, for example, for a 6/8 or 12/8 ballad, we now have a half dozen or more at least to choose from on all the arrangers. Same with all the style categories.
I tend to do a lot of comping, especially guitars, so have to be aware to leave room in the style for that.
Still agree with Diki that it would be nice to be able to automatically mute the sound in the style that is identical to the one with which you are playing the lead line.
The BK9 does have that great Mute button, that will allow you to choose which style parts you want to shut off when you press the button, or control switch.
With the mega memory we have available now, it's easy to create, save and easily access several versions of the same style, if you need more variety than the four style variations allow.
This is the kind of thing we should discuss more, operational features, etc., that are common to all arrangers.