I like the idea... I think it's a terrible waste to have to toss things just because of a pooched battery pack that normally can't be easily replaced. This would certainly help keep things from the landfills.
I hope it can happen with other things too eventually... like cordless tools. I have several drills that, while the drills themselves are in great shape, the batteries are cooked and in a lot of cases it's cheaper to just buy a new drill than to replace the battery packs.
I really don't think there are 18,650 batteries in a bicycle battery unit, unless they're watch-battery size, and then I don't see being able to replace individual ones, there's probably 40 or 50 individual cells that are easily identified and replaceable.
I hate modern journalism, I wonder where they got the 18650 number
i love the idea, but everything i know tells me that replacing one cell in a series parallel array with a fresh one is a bad idea.
over it's life, a battery's capacity and internal resistance change, so it's not only important to match batteries in a pack by exact type, but also condition. otherwise, the cells won't charge / discharge evenly, leading to overdischarge / overcharge, or, if managed by the bms, drastically reduced performance (basically all cells are limited to the worst one's performance).
still, the concept is fantastic, so i hope they found a way to work around this issue!