I don't think there is anything in the QtWebKit settings APIs that would allow me to do this. It is of course technically possible to do it, simply by storing the values in an appropriate format, but I'm not sure what that format would be. It would depend on what else was to be stored besides the zoom level.
Well, I was not ready to suggest that people make it their default browser.
The cursor key handling was only implemented in the last update, following implementation of custom key event handling in the components.