Not possible to ask for more with BMWFS, all lease buyouts are now handled directly through dealers as of about 5 months ago.
CPO sales are hot, so big discounts off of the contract buyout aren't common now. I think it's unlikely you'll get a much better deal. That said you should negotiate directly with the dealer to see if they will agree to turn the car right over to you, they can actually make more money selling the car to you than to the owner (they pay a premium for the car from BMWFS to sell it to the original owner).
Hope that helps.