I have an idea: Wouldn't it be better if there was an app for touchscreens that predicts which letters are least likely to be typed next and shrinks them!
I've heard a few times before that the iOS keyboard invisibly grows the touch target on the letters it predicts are most likely to be typed next. Unfortunately, my quick attempt to find a source failed.
Wouldn't that destroy the muscle memory involved in learning / remembering where the keys are on your soft keyboard?<p>Nonetheless, if you believe you could make this work, why not do it yourself?
Windows used to have menus that would re-arrange themselves and show most-used choices at the top a few versions back. People hated it. Destroys memory.