Firstly, different peoples' concept of perfect may not be the same as other peoples' sense of perfect. As you suggested yourself, to your first friend, the 'holy trinity' might be perfect for them, but not for your other friend who prefers a zoom covering the same range.
Secondly, it will depend on what is being photographed, by who, the prevailing lighting subject, and action conditions. A wide angle (e.g., 28mm) prime might be better in some subjects and conditions, while a versatile telephoto (e.g., 70-200mm) zoom might be more practical for other subjects and conditions, depending on who's photographing, what specifically they're shooting, and what their preferences are for doing such shots.
As far as your suggested 18-300 f/1.2 is concerned, you may be prepared to pay $10K + for, and be strong and fit enough to carry such a (perhaps 10 kg) lens around your neck for several hours, but there are probably other who wouldn't.
There is/are one or more 18-300 zooms in existence (Nikon AF-S DX Nikkor 18-300mm F3.5-6.3G ED VR , Sigma AF 18-300mm F3.5-6.3 Contemporary Series, Tamron evemn make a 16-300mm F/3.5-6.3 Di II VC PZD ) with a more modest max.aperture, because that's probably what the manufacturer may have considered to be the best value / balance of price / aperture to be sellable, portable, manufacturable. Again, as you said yourself, the issue of sharpness for such focal length range combo at F1.2 could be difficult to achieve acceptable sharpness performance for a reasonable price, and portability.