Let me try to explain what Donny is asking in terms of relating to the current synth/workstations (not that he needs me to explain for him).

Take the Korg M3 for example, this workstation has soft pads on it and it has a Karma algorithm in it that will actually play backing tracks. There are many sequences for many different styles of music. When you press one of the Pads and / or chords on the keys, the bass will follow you. It is not an arranger, but you can get some really good song results this way.

I have this feature on my Roland G6 workstation. There are built in arpeggiators that sound just like backing tracks on an arranger. However, there are NO intro or endings; unless you sequence them yourself. Actually, you can do fills and breaks by using multiple Arps and trigger then just like you do on a break.

The main difference between a workstation and an arranger is you have to work a lot harder on a workstation to get the same backing track song results. This is the bread and butter for an arranger, so it's much more natural and transparent.

The way WS address arps and loops is like stepping back 15 or more years in arranger technology. They ALL need to be cued up one bar in advance of when you want them, whereas arrangers have had the ability to switch in fills and breaks instantly (allowing you, by varying when you call them, to get more variety from them) for donkey's years.

Cuing up stuff in advance is an utterly different playing paradigm than simply being spontaneous. Once you have experienced the latter, it is SO hard to go back to the former....

And, sad to say, but once again the specter of unprotected data rears its' ugly head with the arranger/WS split in musical emphasis. I would hazard that it isn't THAT difficult to convert the MIDI data from a style's output into an arp that could be played on a WS. But it isn't automatic, and would require gobs of work to do to as many styles as one would normally want to be able to gig on one SORT of like an arranger. But Yamaha, Korg, etc. are VERY unlikely to do this work for you (and who of us has the time or skills to do it for ourselves) as impossible as it would be for them to make even a break-even point for the work, let alone a decent profit...

We are stuck, possibly because of our own actions, with the fact that the musical emphasis difference between WS's and arrangers is unlikely to change, ever... You want oldies, you want ballroom, you want almost anything but modern music patterns, you are going to HAVE to stick to arrangers, or be prepared to work for MONTHS (or longer!) to import these legacy musics to a WS. And you are STILL going to have to completely change the way you play, to allow for advance cuing of everything as well.

Best of luck!