I'm still confused by the 16-80 though, the reviews are slightly less critical than initially but I cannot get a clear answer if it's as good as the 18-55. It seems that the center is sharper but the corners are worse and the wide ranges, 16-20 and 55-70, which would be half the reason to get it over the 18-55 besides WR, are the worst.
I haven't performed any rigorous comparative tests, but your summary seems consistent with my subjective experience.
I've always been quite pleased with the sharpness and contrast of the 18-55mm as well as the other Fuji zooms I own, and that's not my reaction to the 16-80mm. I haven't used the 16-80mm much yet because I haven't been traveling since I acquired it, but it's clearly not in the same league as the 10-24mm or the 55-200mm and,
at its best (e.g., stopped down to f/8), I think it might be comparable to the 18-55mm within the same range.
The weather sealing appears to be excellent; that's one attribute which definitely isn't a disappointment. I'm also very impressed with the image stabilization, which is more effective than any of the other Fuji zooms I've used by maybe one stop. And I like the form-factor: on an X-T3, it doesn't really feel much bulkier or heavier than the 18-55mm (although of course it actually is both).
My advice would be to wait until it becomes available as a rental—that shouldn't be long now—then try it for a week to see how it works for the kind of shooting you do. Or perhaps the
OpticalLimits (Photozone) site will review it; I've found their analyses to be quite reliable.