I can't see it because there is no heritage of mid-engined Alfas... So the 4C gains attention as was the intention but it doesn't carry through to the Giulia, which is not a mid-engined sports car and has little in common with the 4C.
Sorry. Got to call foul on that one. Your thesis seems to be about what is or is not compatible with the brand or a halo car etc. You and I don't need to agree on our favorites but Alfa Romeo have built a lot of vehicles and configurations of them. The example *you* chose to make a point using is a clear tribute to an Alfa Romeo I have always lusted after and I don't seem alone (dealers' walls were plastered in pictures of it before there was any inkling of the 4C). The Tipo 33 Stradale, a mid-engine lightweight low volume "halo" car that I not only have no hope of ever owning, but I have no hope of even getting into if I stole one (I'm 6'4"). I do fit in a 4C... I'm sure Alfa made some concessions to making a marketable "halo" model when they made it relatively (a) affordable (using an engine out of a volume production car) and (b) possible for potential customers to actually get into (fitting their sandwiches in as well remains a problem, although at least they get toasted).
You also suggest a particular direction to go in from the Giulia sedan. Alfa has history of everything from stripped down race cars to luxury cars with varying degrees of practicality - the road going "luxury SUV" is a ridiculous label for a less low slung, more comfort and space oriented vehicle than road cars had been converging on. The marketing people needed a label, fast, when people wanted not a Camry and not a Hilux, and certainly not a Tarago.
But back to Alfa. Touring would have been happy to build a "SUV" (they would have considered it a limousine) for you on your 6C chassis.... Or build a low slung thing with a back seat, or yes, build something on a SWB chassis with no back seat and no roof.
But of course there is only so far you can stretch a platform. I think Alfa have managed to pick a good middle ground to start from with the Giulia. Lets see where they can take it and what else they come up with, but there is no denying where the volume is, so that's where they have gone first, and need to prove themselves. I'm not sure what exactly the road going SUV needs from its platform that the Stelvios doesn't have? What is the Macan's magic ingredient? And Porsche's SUV heritage is considerably more lacking than Alfas. On the other hand, if Alfa *had* made a sports car on the platform, would you have informed us how it was doomed because Porsche builds proper sports cars not based on sedan platforms and Alfa needs to try harder? Fair point actually - but isn't that what the prancing horse brand is for (barring the light-weight, small engine capacity approach - hmm - I present - again - exhibit 4C)? But maybe that should have been an Abarth