Well, whatever works…

But is there any Roland arranger left other than the FP that uses the old system?

Thing is, you’ve already got what I think was the high point of Roland’s arranger line. Everything else you look at from this point is a huge step back, even the FP unless you are a decent pianist (which you admit you’re not) because, while you can use the old system on it, you can’t load any of your older styles on it, or edit the styles it comes with. Other than a great piano sound and a great action (for a pianist), I’m hard pressed to think of anything the FP brings to the arranger user’s table…

I rather fear that Roland have decided that, to compensate for lost revenue by no longer offering even mid-line arrangers, they are going to go with that paywall and lack of editing, forcing users to buy their styles. That’s a hard pill to swallow when the DGX’s still allow a pretty full featured arranger along with a decent piano and action (which you don’t really want).

Maybe if full chords are out, try the Yamaha system. I rather think that’s the only forward path for how you play… but with a BK9, I honestly think there’s zero chance of anything from Roland better, so why not just stick with that..?