While my preference for having 28mm on one end of my main lens is clear, objectively I have to recognise that a 20-70mm f/2.8 could be very useful to me, as it would have the potential to replace simultaneously an UWA and a standard zoom lenses.
I doubt I would go for it, as I imagine myself more likely to jump to prime lenses, within a few years, but I'm certain such a zoom lens could make many, many users happy.
I can make you a 16-600mm f2.8. Not problem. I can whip out one on my optical lathe in about a week. Do you want white or black exterior? I just need a $5000 deposit and the remaining $20,000 will be due upon delivery (which will cost $1000 because of shipping weight and insurance). Bitcoin only. Call me!
That would actually be very cheap.
A 600mm f/2.8 prime could probably cost 25k alone
I really, really, really wish Canon would copy Sony and make a 50-150mm f2.0. I've rented one just to evaluate it and it's an incredible lens that covers such a useful range. Excellent for indoor events.
(...)
That lens along with a 15-35mm and a 300mm 2.8 are all anyone needs for events, concerts, sports, weddings, and portraits. It's not much heavier than a 70-200mm 2.8. The f2.0 speed and shallow DOF are worth the cost.
I tried the 50-150mm last year. Having 50mm on the telephoto zoom is interesting, but the wider aperture didn't really excite me. I don't know, I'm also the kind of guy who doesn't bother to own an 85 or 135mm, and covers everything beyond 70mm with the 70-200mm f/2.8, so I guess I don't care that much for shallow depth of field. I always found f/2.8 to be enough from about 85 onwards.
I also don't use the widest aperture of my 28-70mm f/2 that often, so there's that...
The FE 50-150mm f/2 weights about as much as a traditional 70-200mm f/2.8, like the EF, and the size is pretty similar too. It's manageable, but these new 1kg 70-200mm f/2.8 lenses and, specially, the original RF 70-200mm f/2.8, that takes less space in the bag, are winning my heart. I can now carry a lens
and a camera body where I used to carry just the 70-200mm. That's pretty amazing.