There was as a guy a while back on here who took out the plastic tub and custom fabricated a metal one and got a solid 3-4 more inches of depth from the cubby, you might lose some sound deadening though if you start messing with the padding under the cubby. I think he did it to mount an ARB compressor/speaker amp back there.
You might need to worry about heat if you start messing with the sound/heat shield.