My understanding of the AF/TN and the possible BF flights via LAX and SFO respectively is to move passengers between Metro France and French Polynesia. The stops in LAX and SFO exist because there is no aircraft in existence that can fly PAR-PPT nonstop.
The added bonus beyond being along the GC path is that LAX and SFO are popular destinations for French passengers that helps fill the aircraft PAR-LAX/SFO and LAX/SFO are large population centers with affluent residents to help fill the LAX/SFO-PPT legs. SAN, as great a city as it is, cannot compete with the aforementioned California markets in the regard.
Even if SAN were to offer cheaper user fees, or even incentives to have the flight stop in SAN over SFO it would be easily negated by the lack of market.
but if TIJ/CBX used instead of SAN, then surely big savings in U.S. charges & San Diego residents & those living between SAN & say LAX, would have nonstop LCC service to ORY & PPT (for Paris, rather than having to go via Iceland)
Way off on this! Travel to PPT is a Niche market, and a very premium expensive vacation. Yes, San Diego area does have people that have the funds to fly to PPT. That is why they travel through LAX. Even SFO(Bay Area) is getting it's first non-stop to PPT in a long time, and it's one of the highest wealth capitols in the world today. Nobody is crossing into mexico, to go to PPT, give it up....
SFO/PPT is French Blue & many of the wealthy around SFO will fly them, as otherwise they have to go via LAX. So think not only should French Blue fly ORY/TIJ/PPT, but think they should also look at ORY/YVR or YXX/PPT. We're not talking daily but rather twice a week.
Another thing, BF should maybe look at is a further extension to Australia, but not SYD. AOM used to fly, ORY/LAX/PPT/NOU/SYD up until take over in 2001, if my memory serves me correctly. A high density A350/A333 could probably not do SFO/Australia nonstop without some sort of weight restriction, so a quick stop in PPT,might work well + it would provide Australians with a nonstop route to PPT.
Also a direct(2 stop) Australia/Paris LCC service with quick stops at PPT & SFO might be competitive with other 1 stops via Asia/Middle East.