I'm not sure if it's possible, but an aftermarket battery with closer to the MB Airs KW/h specs would be a very interesting modification.

The repairability seems to be interesting especially if it leads to framework style upgradability (logic boards, not the ports).

FYI: KWh (it is a product).

I'd bet dollars to donuts that it either treats any battery connection like the stock battery or it fails over to a run like crap mode like third party batteries in their phones.