no, 2000 would need to be master, assign channels to the 2000 accompanimnet midi outputs (I can't remember, I think you could do this on the 2000) and set voices to those channels on the 6500.
To be fair the 6500 styles are far superior and livelier, more interesting than the 2000 presets were, which makes dynamic accompaniment less neccessary than in those days, but I still think it would be a good feature available in the composer.