Whilst looking at regional jet design, its worth bearing in mind that the customer requirements are quite different to those of large, long range jets.
There is no point in SleazyJet and the like, flying for an hour or two at high speed, only to sit on the ground for twenty minutes waiting for a set of steps to appear. If the same journey can be flown a little more slowly, whilst maintaining the number of journeys per day, then some aerodynamic compromises can be made.
One Airbus A320-sized replacement being proposed by them looked very much like an Ilyushin 76 with rear, fuselage-mounted engines. The low fuselage meant integral 'Air Stairs' were feasible, and the two engines nearer the centreline presumably meant that the excess power requirement for single engine operation was less, as the dead engine was closer to the centreline, and less fin and rudder were required to overcome its drag. The high wing also allowed larger high lift devices, less constrained by ground clearance than, say, the A321's three stage flap. The high-lift devices would allow a smaller wing in the cruise and/or the opportunity to use cheaper airfields with shorter runways.
Taking this last point a step further, presumably if both engines were in the fin, either next to each other 'a la' TU-22 Blinder, or one above the other, which as far as I know, no one has tried yet, with the possible exception of the Trident 3B (albeit two different engines), then the engine-out power requirement would be even less. Yes, it would be ugly; yes, it would be a maintenance nightmare, compared to dropping a wing mounted engine, but if the sums add up otherwise, we might see it, as engines aren't removed that frequently.