I too had a similar idea, I was going to have the end tanks cut off and the cores welded together, but I found the OBX for a good price and went with it. Now they are 199-275 if you look on ebay. So you really can go wrong. With what you're thinking I would say its bad for flow, the pipes that are welded together in your drawing will act as a big restriction, so it will go "flow good-restricted-flow good" again, so I would think it would hurt performance rather than help it. As the ATI kit sits w/ the twins they are pretty much flowing just like the drawing anyway, they are both tied together at the plenum.
My 2 pennies take it FWIW.
I say go for the OBX you really can't go wrong with it and for the price they are selling at.
J