Apple aren't a company that does something for the sake of it. Whilst it proved to be pervious to crumbs, the butterfly keyboard was a very clever way of making a minimal laptop. There is a place on the market for practical products and pretty ones. (And the 'Macbook' was stunning)

In other words we shouldn't look at a 5mm chassis in isolation. This 'iPhone Air' will likely be as large as a Max model at the very least. Honor recently shoved a 5000mah battery in their 4.5mm thin Magic v3 foldable. Yes, that has 2 halves to accommodate all the other gubbins but take away the folding internal screen and all that needs and you might have space.

I reckon it will end up with a Pixel-style camera bar across the top of the rear that at least adds another 5mm to the phone. In here? A variable aperture, variable focal length lens of 18-170mm, f1.8-f4.