I think the worry would be dimensions rather than weight. I rang J* last week, and the (Asian) agent could only tell me the dimensions of a 7kg bag - old standard. I think a 10kg bag is the one that a lot of people have with wheels, and many people already use this as a piece of checked baggage.
The Overhead lockers are certified to carry the weight of several 10kg bags - and it is hardly the lockers fault if they do not survive when the aircraft if flown into the ground (CFIT).
Dimensions can be monitored at the departure gate