Must be getting at least close to the lens the long suffering @ahsanford has spent years wanting from Canon! Although from memory, perhaps still a little bigger and heavier than what @ahsanford really wanted ... and with the wrong lens mount, of course
I've considered an 50/1.4, which was always IN THEORY a great lens on EF film cameras in the 90s.
But there's basically two ways to design such a thing:
1. Old school double-Gaussian, which hasn't really advanced much since like 1970. They're small, simple, cheap, but just not that sharp. The EF 50's were pretty soft and low contrast even in the day and are worse yet given both 1) advancing technology, and 2) low-noise, high ISO, fantastic MP count, perfect autofocus all moving the ball so far ahead that the shortcomings of the relatively soft lenses of yesteryear are far more obvious than before. You used to not be able to blame the lens TOO much when film grain and focus were iffy, hand-shake and subject movement adding extra unsharpness as well.
2. New school computer design like the Otus 55/1.4 or Canon 50/1.2. Great image quality even wide open, but huge and expensive: the 50/1.2 is twice the size of the old one.
So, WHICH 50/1.4 would you want? A 50/1.2 down-rated to 50/1.4 is going to be nearly as heavy and expensive. Or, a 50/1.4 that is borrowed from EF, more or less, just as the 50/1.8 isn't that different from the EF 50/1.8's that for 30 years were pretty much the same as the preceding FD 50/1.8's?
The third choice might be something like the 50/1.4 but modernized just enough to add IS (and I'm not sure that's even possible in a double-Gaussian; I don't think I've ever seen one). But again even the 50/1.8 isn't cheap. Would a 50/1.4IS cost $1500? And if it did who'd buy it?
Finally I come to the question of: what is the need? In film days you needed every 2/3 stop you could get. You needed 1600 speed film to shoot 1/30th at f/1.4 in a restaurant with moody lighting. It made the viewfinder substantially brighter too. In such a shot the camera shakes, people move, there's no DOF, and grain made it look like you were louping a bowl of Rice Crispies. But today you can laugh and turn it up to ISO10,000 and shoot at f/4 and shoot 100 frames and be sure that people were still enough in some of those. IS takes care of camera shake too. Arguably if you only had f/4, you'd like the option of f/1.4. But we have the 50/1.8. Meanwhile, do you really need f/1.4 for shallow-DOF shots? I don't think so. Again the pictures are so much better we can present them in 1500x1000 on computer screens, instead of handing around 3x5"s. The lack of other photo flaws lets the shallow DOF have center stage, and the far greater enlargements mean the bokeh is also an order of magnitude plainer. 50/1.8 is quite shallow already in any subject where 50/1.4 would also be shallow. Meanwhile, subjects so far away that they don't pop from the background at f/1.8 aren't going to at f/1.4 most of the time either: just a very very narrow range where f/1.4 gives pop and f/1.8 doesn't. In summary I don't think there's a strong need, even the question of people who want the artistry of shallow DOF.
And if you really just gotta, gotta, gotta have that shallow DOF, the 50/1.2 is right there in the catalog. So now you're not just talking about someone who absolutely needs that shallow DOF of 1.4 where 1.8 is simply not acceptable; you're also limiting sales to those who haven't bought or can't afford the 50/1.2.