That wasn't my point, the UK had to have a means of delivery otherwise the whole thing is a waste of time. The grand slam could be carried by a modified Lancaster and reduced performance in range was accepted. If it couldn't be carried by a modified Lancaster it wouldn't have left the drawing board, Barnes Wallace had many ideas for bombs and other weapons, including ideas which needed planes to carry them that didn't yet exist.
OK, I see your point. The Blue Danube was designed for the jet engined V-bombers (and possibly vice versa).