I wouldn't say it's glorifying normalcy if they stick with normal SHIELD agents; they'd just be showing (relatively) normal people's perspectives on the increasingly superhuman world in which they live. If you don't think that can make for an incredibly entertaining and intriguing narrative, check out a few Gotham Central trades.
I also don't see why superheroes need to necessarily remain unique in their universes. Sure, they should be now, but over time why wouldn't people get used to them? It's the logical way for events to play out if superhumans maintain a consistent presence on Earth over a long period of time. Literally every single one of Marvel's superhero comics published today understands that. I wouldn't be bothered if the SHIELD agents who've been around a while become a bit jaded about superhumans 2 or 3 seasons down the line (assuming it makes it that far). That's where introducing new POV characters occasionally comes in.
That's actually a good point with
Gotham Central--I've been a huge fan of those for a long time, and I understand if this series can work on that level.
There is certainly an audience for it.
However, I'll still insist that there has to be two different ways of doing it. On one hand you have what Fury was doing throughout
The Avengers--basically responding to this overwhelmingly superhuman threat, being "hopelessly outgunned" and trying to balance out a group of increasingly volatile superhumans as a part of his "team." And that's great. It still manages to keep what is superhuman unique in its own crazy world. That's why the Fury bits were some of my favourites. On the other hand you have what happens in almost every other comic-book, where people really act on a level above the people of Townsville. What happens is that those really iconic moments where Spider-Man is fighting the Green Goblin high atop the sky-scrapers of NY become not-so-iconic. And it's not just Marvel Comics; both companies are guilty of it.
Even if superhumans maintain a consistent presence on Earth over a long period of time, they'd cease being "super-human." And that's where all the mutant-prejudice comes in. It's great to have a "David vs. Goliath" story but if you're telling it in a world where there are 10 more like Goliath, his monstrosity becomes muted to the point where his sole narrative purpose of being this unstoppable monster who, upon being stopped,
enhances David's heroism, is lost.
Or, to stick more to my original point, if there's a David vs. Goliath around every street-corner, the Davids would cease being the underdog, and the entire drama of the story would be lost. If they do go with this, what I'd like is if they still regarded the superhumans as these iconic beings--gods among men--and they are the mortals struggling under them. The uniqueness of those superhumans need to exist, even if only to be refuted and ultimately overcome.