Why nobody mentions multiple security deposits (MSD)? You can put 7 MSDs and lower your money factor (interest rate). If you have free cash, use it to lower your interest payment. It works like an 10-12% tax-free return.
I did put good downpayment on my first X3 lease, car was totaled after a year, money was gone. After that I used my cash as MSD only, on second X3 and current X5. It does lower my payments and it's my cash at the end.