For the 50/1 lens, why not? If you can afford a 28-70/2.8L lens, you can afford this.
And if you think it must be big, like the Canon 50/1L lens, take a look at the Leica 50/1 lens. I was surprised to see it looks like a regular 50/1.4 lens.
Why f/1? Why not just use ISO 1600? Now, imagine f/1 and ISO 1600. You won't even need light. (Of course you do; just exaggerating)
What about DOF? Try shallow DOF some time. You will discover you don't need DOF. I sometimes (often?) misfocus and the subject has a kind of soft focus look.
If you like shallow DOF, a fast lens is essential for wide angle lenses. They have more DOF, so you need to open up more. A 50/1.4, for example, has the same DOF as a 100/2.8 at the same distance. That's not that shallow, right?
No, I don't have a 50/1 lens. Just a regular 50/1.4 one.