Regarding the battery alone, I think we should also mention that there have been and are third party batteries both for the FP1 and the FP2. in the case of the FP1, they are just “somewhat” fitting, but there have been third party batteries exactly fitting for the FP2 as well.
Of course, those were certainly produced without any Fairphone involvement (and knowledge). And we can assume that those third party producers are not doing it for charity reasons, so they must have seen at least a good chance to make some profit from their endeavour. Given that the FP3 is selling at a considerably faster rate than the FP1 and the FP2, I would guess there is a good chance we will see third party batteries for the FP3 as well sooner or later. So that might help to prolong the availability of acceptable batteries (although you might expect third party batteries cutting a bit into official FP3 battery sales).