Rear engined airliners
As I understand a big disadvantage of this layout is the difficulty in recovering from a stall because the tailplane is masked by the wing at high angles of attack. Another, particularly on the VC10, was that the centre of gravity was so far back that the tail had to be huge to make up for the lack of leverage.
There was obviously a good reason why rear engined airliners and bizjets were never built with a canard instead of a tailplane, but what would be the downsides of this layout?