Icydock_Tech: I believe you are incorrect about SFF-8087 connectors topping out at 12Gbs. SFF-8087 cables basically 4 independent SATA channels packaged as a simpler connection. A SFF-8087 cable can do 4x 6Gbs = 24Gbs.
To go further, you could use 2x SFF-8087 connections and make use of dual port (DP) HHD/SSD. Granted, DP SSDs are just beginning to hit the market but they are coming and only 7 more data paths are required on the backplane per drive. Your drive socket probably already has the pins. Having DP would improve data read and write performance (can write on one path while reads can concurrently be serviced) and provide data path redundancy.
To future proof the design, use SFF-8643 (mini-SAS) connections for 12Gbs per link (4x) possibilities.