On the other hand - you seem to have a narrowly focused problem that could possibly be solved without spending $6000.
What memory card are you using in your D800e?
I am getting pretty respectable buffer depth using a Lexar 1000x CF card in my D800. When I need speed (I shoot wildlife) I set the camera to 1.2 crop mode (24 mega pixel) and shoot 12 bit lossless compressed RAW – this gives me 5 FPS and over 30 images (that’s a 5-6 second burst – I don’t remember the exact number of images) before the buffer fills. Setting the camera to DX crop mode (15 mega-pixels) the camera will shoot a full 100 images at 5 FPS.
If you are using a slower memory card - it may be worth trying out one of these fast Lexar Professional 1000X cards. They aren’t cheap but they cost a lot less than a D4 and will significantly improve your buffer depth.
Of course, if you need more than 5 FPS and an endless buffer then the D4 cannot be beat.