So actually, due to different licenses, copy-pasting jquery.accessKeyLabel code into OOjs UI would be a copyright violation (and parts of this code are like ten years old so contacting the authors to relicense it would be difficult). Reimplementing it from scratch seems like a waste of effort. I'm just going to make OOjs UI call into jquery.accessKeyLabel if it's available.
The extra hidden dependency is a bit annoying, but eh. There's like three other things in this idea already that will be annoying.