The one contra-indicator I really see on a 70-150/2 is that I've never seen a zoom out-spec primes. With the exception of the 200/1.8 "Eye of Sauron," there's never been a prime that I know of, (or if I'm wrong, at least in the EF/RF lines) with that size aperture.
Talk is free so I allow my my biannual recitation of halo lenses I'd like to see from Canon:
135/1.0DS. This would have perfectly round highlights out to the corners at f/1.4, and have a apodization filter cutting transmission to f/2 that turns those round highlights into spheres. So, in practice it wouldn't be overkill. 135/2 is definitely usable. You'd also be able to use it at f/1.4 if you want circles, and the full f/1.0 would have football-shaped highlights in the corners as most lenses do. Using it with the DS filter would create the best portrait photos and cinema in the history of mankind, though, and give images that you could recognize even in thumbnails. That image there--I know the lens. Physically it'd "only" need a 135mm aperture, not dissimilar to a Canon 400/2.8, 600/4, 800/5.6, or Nikon's rara avis 300/2. It's not crazy. In mass production it'd only need to be a $15k lens, but production might be more limited, and it might only be available for ownership or rental "by invitation" from Canon.
50/0.7. It's not a hard lens format to do. Kubrik had several of them, originally designed by Carl Zeiss for NASA, and used them shooting Barry Lyndon. I mean, the Zeiss design is off patent, you could literally use that, though I'm sure you could do far, far, far better too.
https://celluloidpopculturejunkie.wordpress.com/tag/zeiss-50mm-f0-7-lens/
35/0.95. Others make 35/1.0 and Canon has had periods where it always slightly out-spec'd the competition. The spec specifically echoes the S 50/0.95 from 1961, of their old Canon 7 rangefinder system.
https://www.flickr.com/photos/leicarumors/albums/72157712877553957/ https://global.canon/en/c-museum/product/s43.html