"Not all the air/glass interfaces are even coated, AFAIK, in most
lenses."
I think you'd be hard-pressed to find _any_ multi-element lens, in _any_
camera, in which all the air/glass surfaces did not have _at least_
single coating.
An uncoated surface loses 40f the light. Six uncoated surfaces would
lose 1/3 of an f-stop, a significant loss -- not to mention the increase
in flare.
Prior to WWII, even relatively simple lens designs had most of their
elements cemented in groups, because there would have been too much
flare and light loss if the elements were separated -- even in lenses
with just four or five elements.
Unfortunately, cementing the elements together forces the adjacent
surfaces to have the same curvature, and you cannot adjust the spacing
of the elements. This reduces the number of "degrees of freedom" in the
design, thereby reducing the degree of correction possible.
After WWII, coating became common. It is only because it is relatively
cheap to coat every surface that we have the complex wide-angle and zoom
designs that are so common and so useful.
Thousands of multi-element glass lenses have been designed over the past
30 years. If even ONE of them had a _single_ air/glass surface that was
not coated, I would be flabbergasted.
PS: Have you looked at the front element of the Infinity Stylus Zoom 80
Wide DLX? It's _concave_ -- extremely concave!
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