One minor glitch: when this option is enabled, you add this string: &output=classic&dg=optperm
This works fine unless the maps-button is used just to launch Google Maps without a specific search. Then this leads to an URL like https://maps.google.de/&output=classic&dg=optperm which gives a 404 error. That's because there are no parameters in this URL but the first parameter of an URL has to be appended with "?", not with "&".
So I think this could work if you leave it like it is now but append ?output=classic&dg=optperm instead when there's nothing entered in the search box.
From Ralf: