Just to add my few cents worth here, to the hypothetical scenario.
The piccie is somewhat an artist's impression and is, I will agree, very pretty. But it is more "Star Wars" than practicality. Those canards are really in the way - but it doesn't really look right without them. However more on that later.
The biggest single objection to a canard config in a civil airliner is practical rather than aerodynamic. That LH canard is going to have to be an articulated unit (retract or fold) to have any chance of a normal airbridge engagement. What price a "folding wing"?
The area ruling is totally stuffed with the proposed fuselage format. If Mr B is looking for a 0.95 cruiser then most of the local airflow is going to be transonic at best and with a huge great lump in the "area" just abaft the nose section life in the cruise end of the pond is going to be very draggy.
I agree on all the points about the downflow interference and I can see that the canard wings will probably have little work in the cruise segment and will probably be "feathered" - leaving conventional aft surfaces to do the work. The inference about trim changes are mute, since there is a lot of wing there for fuel and any canny design should be able to effectively reduce time/ burn trim variations to zero.
So we are left with a single wing - probably reflexed (in good delta tradition) doing all of the work in the climb / cruise / descent portions. However the sheer scale (and inertia) of the (proposed) beast suggests that some form of pitch enhancement may well be needed at the lower IAS end to provide pitch authority.
All the newer B aircraft utilise (in some form or other) the concept of fuselage lift at the higher alphas. This is powerfull stuff - draggy, but stable (see flat plate).
As an aside, I have done a little work on this (at the flying modelling end to be sure), but I can attest to the fact that a little bit of turbulence, well forward, at the right time, can modulate the pitch wonderfully on a flat bottomed fuselage.
My take on this is that the canards may well be there, but they will be in the expanding area nose portion and very small. Little prehensile thingies really. We shall see.
I personally doubt that this baby will ever see the light at end of any tunnel. Pity really - she is soooo pretty.
MG