Comment by MrDrMcCoy

I'd settle for requiring the battery specs to be fully available, and that they can't be made difficult to manufacture without good reason.

Ideally, there should be some set of standard protocols/connectors/voltages/sizes, but the manufacturer should only be held to "downward-compliance" with at least one of them, so they can have flexibility in design but still leave a suboptimal standard option available to users as a fallback.