I have three kids with car/booster seats and needed a way to access the storage without lifting the seat. I found a youtube video by "zero to awesome" that showed him making a cabinet with drawers that pull out of the sides for his raptor. I used his concept and made one of my own to fit the sierra. I know this isn't an option for everyone but if you have the means to build it maybe try that, it has worked a treat for me.
Brandon