The elaborate floating crane isn't as Rube Goldberg as it seems. It's pretty similar to the Mars Phoenix mission, but with the engines on the other end. The only real difference is that SpaceX is eliminating the need to pack a parachute by developing engines that can fire reliably and predictably in a supersonic flow. (And Dragon doesn't throw the engines away after landing).

Curiosity isn't required to use the elaborate floating crane, but I'm guessing some feature or requirement of the mission made placing the engines above the craft more appealing than placing them below.