I think people exaggerate how bad QWERTY is. Studies have not consistently found an advantage for one keyboard layout over another, and some studies even show that typists can reach equivalent speeds even with randomised layouts. This suggests that experience and practice with a particular layout is far more important to typing speed than the particular placement of letters. Which is a good argument for keeping qwerty around.

(reducing the risk of mechanical typewriters jamming by not having two hammers next to each other be pressed at the same time),

This story is quite common but there is little evidence that it's actually true. The designer of qwerty actually made a late adjustment to move R next to E (swapping it with period), even though ER is the second most common letter combination in English.