That doesn’t sound like a good idea. Those said DC power might be extremely dirty (e.g. portable two-stroke gas generator) and will basically destroy these delicate electronics without proper filtering (which take up space).
It already has an “emergency charging mode” that takes practically any “smart” power supply, which is way more than even I had asked for.
What I had thought of in the past is some kind of “power pins” on the motherboard that allow for “advanced users” to connect something like an industrial 12V supply to it, since the board is supposed to be able to run standalone.