It could be cool to have a light check-in bag, to check alone on back home trip when I bought so many things or recieved too many presents.
Or to cover my Aeronaut if I'm asked to check-in my bag.
This cover bag as to be light (dyneema or spunbond non woven fabric), easy packable in my aeronaut, with a strong zipper and a luggage tag window. No need of many handle or poron. Keep it light and simple.
It could help in this case Aeronaut, Tristar and the 5kg (11lbs) limit