I wouldn't put any money down on a lease. If you drive off the lot and total your car, that money is gone. If you want to lower your payment. Use MSD's ( multiple security deposit). That money will buy down your money factor and decrease your payment and it fully refunded at the end of the lease ( less any fees owed to BMW)
Also, I think they are marking up your money factor. You could probably get the cap cost a little bit lower.
Current: 2016 BMW X5 - 35i and 2014 BMW 535i
Former: 2012 328i