For those who were interested, or who may come across this thread, I'll post "the rest of the story."
I ended up buying the Trac Vac PTO unit with the "remote pickup" - a 12 ft. length of 6" hose with a handle that connects to the main 8" hose. I took delivery in the early winter and finally had a chance to give it a couple of fair trials the past couple of weeks.
Conclusions:
1. I'm very happy that I got the PTO unit after spending an hour trying to start the wood splitter thee weeks ago.
2. The idea of a floating remote pickup might work with a grassy ditch, but could not in my application with a ditch of varying cross-section and lots of stone in it, varying from gravel washed off the road to 6 to 8" rip-rap. This thing will pick up fist-sized stone with no trouble, but the blower doesn't like them at all.
You really need to manage the end of it to get the leaves lodged in the stone without picking up the stones themselves. That means you really need to recruit a tractor driver because climbing on and off the tractor gets old fast.
3. The standard 12 ft. remote pickup attached to the 8 ft. of 8" hose may work for occasional use, but is far from ideal as the main way of working. The 8" hose is stiff, and the connector is a heavy steel thing that's a real pain to drag around. I'm working on getting a 20 ft. length of the smaller hose and mounting it directly on the blower.
4. Picking up leaves directly is probably a bit more problematic than using the unit with a mower deck. As advertised, it is not a shredder, and while the blower does some shredding if the leave are pretty dry, they are clearly not as fine as if picked up with a mower deck. As a result the bin fills more quickly. On the other hand, I was worried about clogging with twigs getting picked up with the leaves. That has not been much of an issue. Twigs that don't catch in the inlet don't seem to seldom clog the hose, and the few clogs I got seem easy to clear by straightening the hose and giving it a good flip.
5. I've found the unloading issue to be real. Unless you can face the trailer up hill, it doesn't raise far enough to dump well. I've not yet worked out a solution to that.
6. I find it mildly annoying that it's a category 0/1 three-point hitch. Even after building out the pins with as many washers as they would take I still have to adjust the arms in to fit it.
7. If you take delivery in January and decide to test it on piles of wet leaves frozen to the ditch, expect disappointment.
I find the unit well-built, and using it much less frustrating than trying to blow leaves up the bank, especially if there is any wind. But using it to clear ditches is still a goodly amount of work. The composted piles of leaves from my spring cleanup are looking very useful, and I'll have a lot more of them after this fall.
Terry