How much rechargeability really requires from hardware point of view?

I suppose the problem is that there are no standard for tiny magnetic chargers/cables. Every watch comes with their own, and they need be custom designed. For a device this large as much of the charging electronics should be outside the ring.

And another (small?) problem is that you'd need to electrically protect those external pins.

Yeah, this would have been a neat tool for "middle-of-the-night" thoughts, but I don't want a disposable electronic device. I get why it is that way; not having any charging hardware probably makes the device much smaller. But I'd rather it be a bit bigger and rechargeable.

They can still make another version which is slightly larger and is rechargeable; and let people decide what they prefer more.