The only issue with rebuilding the old batteries is being able to source single cells, as the arrangement of having one battery offset is a bit of a pain.
Otherwise it would be a simple replacement inside the battery case.
They are not too difficult to get apart.
Thanks for the video. I think. I'd still rather fly my Solo than my DJI birds and all that DJI firmware crap. So fly them until they drop, fly them until the last battery has pooped its last pop, fly them until they have flipped their last flop. (sorry been watching too much Dr. Seuss)... Perhaps with all the great DIY types in the Solo community necessary parts will rise from the ashes.