I imagine it should not be tough to test this theory, they don't need the whole 787 for that, just a small section of a fuselage with all the relevant tubing/insulation/electrics, etc.
Not even that, all that is needed initially is an ELT, or perhaps even just some of the battery packs.
I'm not sure what the 'Current limiter' is, but that is not a description I would use for a 'conventional' fuse so I suspect it is a self-resetting fuse of some sort. These work by increasing their resistance with temperature and that increase in temperature is caused by resistive losses due to the current flow through the device then, as the resistance increases, the current drops or limits.
If the sizing of that device is wrong for the equipment, or the device was faulty, and it is in thermal contact with the battery I could imagine a scenario where it is possible to get a combination of over-current and temperature where the device is cycling 'on and off' (I know it's not quite on and off but you get the idea) and the combination of a hot day, hot limiting device and self-heating in the battery due to the fault current could be, over time, that the Li battery is heated to the point of thermal runaway.
How's that for speculation from someone who doesn't speculate?