It's exactly the machine I've been looking for, but unfortunately practical/logistical issues (seller states he won't ship, I live across the Atlantic, and my lack of French means I have no chance of discussing anything with him) mean it will remain just a series of tantalizing images on my computer screen.
You also remarked, "...with the possible exception of the later cheaper 'Diamond' range which have smaller pillar and plate motors...." You can safely delete the word "possible"; my Pathé/Diamond Diffusor (my profile picture machine) barely plays one of the 11.25" disks on a winding, and not all of those. Given that I have a low-end Pathé cylinder machine with a similar problem, I've been rather fixated on Pathé motors, determined that when I do finally latch onto an open horn Pathé disc machine, it will play all my records without such issues. I've been especially concerned that they all seem to be single-spring--hard to tell from an eBay listing or what have you whether it's single-spring like Edison diamond disc single-spring, powerful enough to handle whatever is thrown its way, or single-spring like the motor in a Victrola I-I that once graced my home, barely strong enough to handle a single routine record on a winding.