I like the idea, and I suspect gaskets will be the solution they go with, with the back cover applying pressure to the gasket to create a seal. but the EU regulation specifically says that no expertise should be required and you should be able to do it with commercial, standard tools (i.e screwdriver). I don't think they could make single-use gaskets where you have to purchase additional gaskets from the OEM. I suppose they could come with the battery itself, which the EU requires OEMs to sell for 5 years.