Provision for weapon mods?
It sounds a bit urban legendy to me.
1. Supersonic stores separation is nontrivial.
2. At the time this would have been considered, the absence of a targeting radar would have put the accuracy in the "all weapons will hit the ground" realm. Close counts in horseshoes and thermonuclear bombardment, but there are limits.
3. Survivability would not have been much better than a Vulcan. OK, you're moving faster; but you have no EW whatsoever, not even situational awareness.