I may be wrong but I'm betting that the 32 hubcaps will fit over the 33 wheels. Then there is the better under hood detail of the 32. While your at it...posable front wheels...possibilities are endless. Might I suggest two-tone blue dark with sort of a dark tan or maroon upholstery?
I did a build up of the Gable car J-567 (Clark Gable never actually owned the cat but used it extenively) about 30 years ago. It came out well though much of the filler has shrunk. Keep in mind all I had at the time was good old green stuff. The way you describe doing your work is exactly what I did years ago. I look forward to seeing your progress, even if you abandon the project. This is coming from a guy who took 15 years to build a Judkins Victoria! Best of luck.
I would encourage you to check out the current photos of the Cooper car. If you PM your address I can get a very good article about the two short wheelbase Duesenbergs, AKA (but not from the factory ) the SSJ cars.
Once upon a time I used black spark plug wire (1:24 scale of course ) for fender welt on a Cord Sportsman I was building. I think it came out looking spot on. Maybe consider that? The Phaeton is looking excellent.
It is so exciting to see kids getting into the hobby. I'm hoping that I can get my girls started. I think I started when I was about 7 but what do you think is a good age for kids to begin building? You have done well getting them involved and their workmanship is excellent!