That is your opinion, which I respect, however the lease vs. finance vs. cash purchase decision is a complex web of facts, assumptions and personal circumstances so there is no correct "across the board" answer. No matter how ugly you believe BMW FS's residuals are you need to run the numbers and then make an educated decision. Below I posted a very simple analysis (and one based on a host of assumptions), but it illustrates my point.
In Scenario 1, it runs the base lease vs. finance decision based on BMW FS's current rates. At the end of three years, you would have to sell the car for just over $52k to breakeven versus the lease. This selling price equates to a 52% residual vaule - could be a decent risk to take.
However, in Scenario 2, if you decide to take advantage of the multiple security deposit option to buy down the lease rate, then the breakeven selling price versus the lease jumps to $55k, or the equivalent of a 55% residual. This may not be such a good risk to take. BMW FS had been running 56% residuals on 3 yr/12k leases for the E60 M5, and dropped that to 50% for the F10 M5 lease so it is likely that they we losing money with a 56% residual.
At the end of the day, each person's level of risk tolerance is different. One person may say it's worth going the lease route in order to know with 100% certainty what their out-of-pocket cost will be. Another person, such as yourself, would prefer to take the market risk for the opportunity to pay less. To each their own, that's what makes the world go round.