Funny - that reminds me of the early Mac a friend of mine had in university. It didn't have arrow keys. Looking up "cursor" in the manual referred you to the fine mouse. Word processing was a huge pain on that machine.

I'm a big fan of gestures, but I don't think they work well to replace arrow keys.

First of all, you'd have to have gestures for all of the modified cursor keys. Shift+arrow to select. Ctrl+arrow for moving word by word. You could implement this by allowing (e.g.) shift+gesture, but this will probably be awkward on the bus. So you probably need more than just four directional gestures.

Secondly, the gestures would have to be able to handle key repeats. For instance: keep your finger on the screen after the "cursor left" gesture and the cursor keeps moving left until you remove your finger.

If you overshoot, or if your gesture is misinterpreted, you now have to correct for the effect of the wrong gesture in addition to re-doing the original gesture. It's like typing in ssh over a slow connection.

If your position is off by only three or four characters, you have the choice performing a single cursor movement gesture three or four times, or using a repeat gesture and risking overshooting your target (probably by three or four characters again).

That's a lot of physical hand movement as well. I imagine it won't be comfortable.

Plus you have to keep moving your hands to and from the keyboard.