Nice trip! I've done the "Isolation Traverse" part of your trip twice in summer conditions - the first time mid-September, 2003 and the second August, 2016. These days it's hard to say if it gets done more in the winter than the summer....probably a toss up. Regardless, it's a stellar summer/fall traverse and in some ways I prefer it over the Ptarmigan. It's cool to see folks like you coming from out of state and not seeing a soul while you're out there! I definitely concur with the "lessons" you learned about late season travel.
In 2003 we traveled north-south. I was with my friend Joe Stock and his father who is a geologist from eastern Washington. Not much info back then...just the Beckey guide (2 sentences), maps, and a little word of mouth. Joe is particularly skilled at drawing traverse lines on maps and I remember marveling how perfectly our proposed line panned out. We both had lots of experience on either end of the route, but had never been around Isolation Peak before. I remember being shocked when we observed the glacial remnants and permanent snowfields around Wilcox Lakes were mostly gone (they're prominent on USGS maps). It's going to be interesting to compare older maps to new ones when the next Landsat survey gets done.
In August, 2016 my wife and I traveled south-north which is the way it makes most sense to ski. In summer, I think I'd recommend the opposite direction. Isolation Peak is harder to climb up than down and the flow on foot feels better north-south. Either way, scheduling a camp in the meadow at 5600' below Early Morning Spire is highly recommended...probably my favorite in the park...with awesome views, bubbling streams and wicked bouldering!