I know you said you are set on the Patagonia River Walker, but you might consider a pair of Korkers. With them you can quickly change from felt to rubber to studded rubber to studded felt as the conditions dictate.
I love the Boa lacing system too. As the boots stretch as they get wet a quick turn of the knob snugs them up. And they come off in a snap. Of course, standard laces are also available.