One of the more noticeable weight reduction methods that Crye used in the design of their JPC was the use of a skeletonized cummerbund. This design maintains full MOLLE compatibility but removed every last bit of unnecessary fabric. Thanks to Egg Roll, the wizard of Extreme Gear Labs, you can have a similar cummerbund for your plate carrier.
Extreme Gear Labs recently showed pics of a cummerbund that is compatible with the excellent Shellback Tactical Banshee PC. The cummerbund is constructed with Murdock jacquard webbing and features 2 vertical stiffeners to help it maintain its shape.
Check out the Extreme Gear Labs Facebook Page to keep track of all the EGL Skunkwerks projects.