keesj- note the designs have a far greater vertical element than your canted tailplane tips. Rear engines give a rear c of g which requires a far greater fin. I would suggest your first design would have little directional stability. It's all very well for these designs to point out an unobstructed wing is 'more efficient'. It is leaving out the negative side of the design where engines on the wing provide a lot of 'wing bending relief' making the wing structure lighter and simpler. It is interesting that the 'engines on wing' formula (737,757, A320 series) was found to be far more efficient and successful than the rear engined designs (BAC1-11, DC-9 series). Even the Russians have dispensed with rear engine designs and concentrated on 737/A320 planforms with their latest designs. Perhaps a chase after maximum theoretical efficiency is not the most cost efffective way.
I think the next step will be revolutionary, on the lines I suggested. The disadvantages of the traditional tailplane at the back/standard circular fuselage/engines on wing can be overcome. Lifting body, no windows, smaller wings, canard, engines buried within fuselage at rear with noise attenuating B2/F117 type ehausts- then you must have fantastic gains in efficiency and noise. Why would you need windows when the whole sidewall can be large curved LCD screens of the outside view, floor to ceiling? How fantastic would that be? No asking someone to get their head out of the way! The video technology is almost already on us.