There were a couple 787 tail barrel sections parked outside the office building today. Comparing those to the published pictures of the Ethiopian airplane, notice forward of the aft door, there are a few windows and then a 'missing' window? The 'missing' window is the break where the fuselage pieces are joined. At least externally, the worst of the fire damage appears to be aft of that joint.
Fire doesn't care about manufacturing joints, so it might be premature to rule out significant damage forward of the tail break. I wouldn't be surprised if not only Section 48, but also Section 47 is deemed unrepairable and is replaced.
Again, not knowing what the internal damage looks like - I'm leaning towards the most cost effective fix being to replace that tail barrel section. Either on site at Heathrow, or if the GSE is too complex, a temp fix to get it back to Everett or Charleston where the tooling is available.
I would agree that it's not going to fly out of Heathrow in a factory-fresh state. I can't see a permanent repair being carried out, whether or not it involves replacing major parts of the structure, al fresco during the British autumn and winter.
Even if it's a $100+ million price tag, compared to a new 787 it would still likely make economic sense (recall the A380 $150 million/18 month repair bill after the Qantas turbine failure)
Not that economics is the sole consideration, any more than it was for the Qantas A380.