In surround configuration, the radios are reconfigured to a one-way dedicated 5 GHz connection from the Arc to the surrounds.  This requires a series of handshakes to get right, which is why adding surrounds takes a bit of time.  The reverse happens when the surrounds are removed.  So therefore, a quick toggle is not possible.  They could place a hot button that does the add surrounds/remove surrounds at the touch of the button, but that is not going to speed up the actual process, and doesn’t save much from the system menu commands we have today.

An alternative would be allowing one to mute the front device and just play out of the surrounds, which would appear to be easier to do, but I defer to the actual engineers on the practicality of the idea. 

Do they have the same handshaking if you have everything network wired?

Yes. It’s part of the function as surrounds, and not because of the network physical configuration. It’s also why, in a ‘wired’ setup, you should never have either the surround speakers or the Sub as your ‘wired’ component. The nature of the connection is different.