Kirk
Never thought of that.
A little background on Capture One might help.
There are basically two ways of working with images in Capture One. Either as a catalog or in sessions. I can't see anyone using both a CO catalog and a PM + catalog. Sessions is folder based and stores all of the images adjustments, previews, thumbnails and metadata, etc in a series of subfolders under one parent subfolder named Capture One. This is similar to the way On1 does their so called catalog. There is one Capture One subfolder in every image folder regardless of how many images or the image types such as raw, jpeg, tif, etc. If there was a way to simply ignore this Capture One folder that might help.
As to to having file names that are over 260 characters long because of deep hierarchy should be of no concern. There should be the parent folder which is always a 4 digit folder like 2019, then possibly a sub parent folder such as New Zealand, then the image folder - longest one I can find is 70 characters, then the image filename which should be no more than 80 characters. There will be nothing below that if you completely ignore the Capture One folder.
So to reiterate, you can ignore the Capture One folder and everything below it when considering hierarchical filename length. I assume that Capture One is storing the metadata in some of those subfolders as they don't write metadata to raw files, however, I have no idea PM+ reads the metadata from the CO files.
If you need to be reading those subfolders and they have to be included in the hierarchical file naming I can always rename the longer ones.
Bob