Trying to juggle a mini PC, a small monitor and a small keyboard, in the small confines of an airplane seat? At that point, I think the answer is to just get a second laptop that has the power/battery requirements you need. So much easier to deal with, and likely lighter to carry.
I suppose you could also try getting a Microsoft Surface - hang that from the seatback, and instead of the typical cover keyboard, use a Bluetooth keyboard.