"I would have preferred a more "classic" shape to the back of the action"
Not sure what you are referring to as Classic Shape. Predominant shape for most non sidelock doubles is a Flat Back. This is certainly far & away above the flat look. IO also like the rounded corners of the action.
For round action triggerplate guns I always thought the Dickson/David McKay Brown was very handsome & hard to improve on & for rounded action boxlock guns, Westley Richards guns featuring the "scrollback" action in either the standard A & D or droplock version
are a couple of "classic" styles that come to mind.
There are many other ways to finish off the back of a boxlock action in a classic manner. Douglas Tate's book Birmingham Gunmakers shows some other examples, most all a bit more subdued than the Beretta 486 shape.
For what it's worth, I've hunted with traditional square actioned boxlock guns & sidelock guns & one round actioned triggerplate gun & I don't think the action shape has anything to do with "ease of carry" since I rarely carry a gun in the crook of my arm or by grasping the action. I do like the looks of most round action guns.