FB, thanks again.
Having had some involvement in the early service intro of Concorde, there's an interesting parallel with the B: Concorde's nominal payload (100 pax and bags, 20-25000 klb) was a tiny fraction of TOW (408 klb IIRC), so very small percentage increases in OEW, or declines in aero-propulsion efficiency, could wipe it out. And TOW was maxed.
Likewise, the B's weapon bringback is a small fraction of VL weight, which cannot itself be increased without upgrading the entire propulsion system - engine, fan, transmission.
Conversely, if you look at history's more successful aircraft, many either started with a very healthy payload margin or were adapted through-life to have one, through higher operating weights and more power.