I think Taptic engine + force touch is the key (ahem) to such a scenario working. If there were little localized bumps every time my fingers moved outside the

I think Taptic engine + force touch is the key (ahem) to such a scenario working. If there were little localized bumps every time my fingers moved outside the area of a given letter, and if the keys could tell the difference between resting, setting, and actually typing, then I'm not sure there would be any problem.