At first I thought it would be good to leave the W pipe because of that, but thinking further about factory setups, I remembered that the throttle body dumps straight down against the 'floor' of the manifold like a carb (some even have ribs right under them that the flow collides into). Now which is better that far up stream is beyond my knowledge...I know who to ask if someone else here don't know for sure. But I doubt a D could draw it hard enough to make any real difference that mattered....?
I was thinking- 'To take advantage of all of the things that are already around'...all we would have to do is build a thin aluminum box, weld an eBay adaptor on it and the rest (throttle body to brain) is laying all over the junk yards.
I'd like to play with any of the several options but I'm not sure what has priority over what for you. I don't want to beat a dead horse here ;-)
Split the difference and remove the upper half of the mix unit...?