A great thread indeed.
Even if a short term fix/containment of problem battery can be agreed with Boeing and the FAA, many or most airlines may not elect to fly the 787 in this state.
Just too many issues to deal with using the short term fix/containment, if a battery fails in flight it will not be available to do the things it was put there for so could make many diversions and much more press coverage etc etc etc !!!
Talk of 100/150 787 batts have been replaced up to this point and the recent events in the press, plus any other events that may not be in the public domain, if the 787 goes back in service without the root cause fixed and has any more serious events with paying passengers on board, history may show it would of been better and cheaper for the 787 to spend longer grounded.
My guess with so much info coming out about how Boeing and the FAA got the 787 certified in the first place, the "A350 plan B" type deal will be the one that gets the 787 back in service.
The cost to the 787 project will be a monster, but as previous posters have mentioned, it could of been much worse.
Good luck to the Engineers trying to understand and fixing the issues.