That's only because the launher does not support the full screen mode. Just like MicroB, for that matter. You don't need that feature, all you need to do is tap on any empty space (to avoid hitting a link) to bring up the soft expand button in the bottom right and tap that button to switch back from full screen. Just like MicroB. In fact, most of your requests can be answered in the same way. On the other hand. That sounds like a reasonable feature. That's what the stock Maps application does. In case you haven't noticed, the address bar also doubles as the search box and already has the option to add search engines.