Thinking about these, the only big advantage of the rear-engine/T-tail config seems to be in avoiding the lack of under-wing space for the engines
I have not yet seen the advantages of centerline distance debunked.
So, reducing the question to the absurd, what about an A380-type aircraft with a high-wing, and 4 Trents (or GE poor copies ) hanging beneath them? What's wrong with this picture?
What about An-124-300? Or remember that An-225 is the only plane bigger than A380, although with 6 engines rather than 4?
There are plenty of high-wing underwing quadjets. Lockheed C-141. Lockheed C-5 - the original high-bypass widebody. Il-76. MD C-17. An-124.
And yes, the civilian Bae-146.
Bae-146, at 26 m wingspan, is small compared to plenty of low-wing narrowbodies. Whereas C-141, C-17 and Il-76 have wingspans over 50 m, and C-5, An-124 and An-225 are yet huger.
Would a midsized high-wing civil jet make sense?
As for tail, while An-225 has special considerations (piggyback loads) requiring H-tail, An-124 is notably different from C-5 in having a low tail. Which tail works better - T-tail of Galaxy or low tail of An-124? Can Galaxy be deep-stalled?
Oh, and once An-124-300 is in production, those 4 engines on airframe stretched from baseline hopefully mean Soloviev has bigger high-bypass engines available. Those would come in handy for An-180 and Il-98 as well.