While I cannot provide an overall generality of northern vs. southern Quet portages, I have some perspective as I took a trip 2 years ago (with the doctor's permission) while needing ankle tendon repair surgery.  Thankfully I could typically walk without pain, and my brace still allowed me to use my boots, though I did have to buy a size larger to accommodate the extra volume.  After a week of ankle-sucking mud, I was glad I scheduled my surgery afterward.  Make sure your ailing friend tests whatever boot, brace, etc. is needed with trail socks, boots, and pants.  You don’t want to find out something doesn’t work in the parking lot, dock or at the first camp.  Also, I recommend a pair of hiking sticks for balance & tricky portage situations.  Finally, modify your planned route to about 75% of what you normally do for a similar duration.