George MacKay would work but then again he is too much of an unknown at this point. I doubt DCEU wants to go for a lesser known actor in the role even though personally I wouldn't really mind it but then again Warner Brothers as a studio I am sure they probably want a bigger name that's all I am really saying. I mean I can see Reeves and DC also wanting to go with a bigger name actor in the role of The Joker especially if they want to not only draw in a much bigger audience but can MacKay pull off Joker? That is also the million dollar question now isn't it?