I already did that last year.....which lead to the creation of the Uber 2x12.
Randy Jackson was at our shop and we were doing live play testing, trying to come up with a stadium back line for him.
We tried all sorts of configurations. What we ended up with was three stacks. Each stack was a Neox-212T lying on its side, with an Uber 4x10 on top, powered by a GBE1200. Man, three GBE 1200's going through six cabs at the same time. I played through it with my USA Lakland 5 string.....OMG..the volume.
Anyway, he liked how the 2x12 rounded out the bottom so much, we decided to build the Uber 2x12.
I'd never have the need for such a setup though...with my gigs. I play mostly R&B, latin etc. Two months ago, I did a progressive metal gig though, with a guitarist from a band called Fates Warning. It was a loud and busy (mix) stage. Still, the one 4x10 was plenty. I did switch to my Ken Smith though.....as it cut through the "din" on the stage much better.