I'm surprised that after 4 responses no one has mentioned this, but there aren't 6 receivers and a back. There's 2 TEs, 2 WRs, and a back. The guys spread out wide on the line are TEs and Ts and the Ts aren't any more eligible than if they were lined up next to the Gs.
I don't know what package subs you can do, but the formation is like this with the QB in a SG (monster) or under center (E&H).
I'd say you could easily sub out the TEs for WRs, but seeing as how the primary plays in this formation are screens, I don't think it would be very beneficial.