The biggest problem now is that if the quantity is small, only aluminum alloy materials can be used. but In order to remove the battery conveniently, the cover plate needs to be plug-in, but it is difficult to insert both ends of the aluminum alloy. If plastic materials are used, a mold is needed, and the quotation given to me by the mold factory is relatively high, so we must stock up a lot of cover plates. We are trying other solutions.
We don't need a fully cover systems with fixations, the simply cover plate who can be adjusted to close the hole (initially build for other of your frame ?) will be enough for the majority of us i think, it's not absolutely necessary to have lips to manage water infiltration, we can do it with thick self-adhesive plastic plate. Alike done on my E10, that's working perfectely since 2 years. true building in alloy is not so difficult, it's just pity on a carbon frame. In add it's more heavy (to have strong).