Thanks, everyone, for weighing in.
To respond to your questions, it’s flight only, and as I got a great deal when I booked it and (pending no further travel restrictions in the interim) fully intend to travel on it, I would like to keep the booking rather than convert it to an FTV and rebook (especially as LHR-LAX/SAN-LHR is now selling for more than double what I paid).
While the EI-operated CDG-DUB flight is currently still operating, with EI suspending the route from DUB-LAX, there are now no direct flights between DUB and LAX for my dates; AA operates with a stopover. In going into MMB and clicking on the “rebook my flights” option, it gives me the option to change my flights to CDG-LHR-LAX on the same day, but my preference would still be to drop the CDG-LHR leg and originate from LHR. Rather than insist I preserve the CDG-DUB leg, which would serve no useful purpose, as it would then require BA to route me CDG-DUB-LHR-LAX (albeit good for the TP balance), could I reasonably assume that common sense would prevail (never a guaranteed assumption, I know), and suggest I start from LHR instead?
I should also like to hope that with the LHR-CDG sector cancelled on the return leg (although I was offered the helpful suggestion from BA’s HAL that the best alternative would be to book me onto an alternative flight from LHR-CDG that departed 5 minutes before my flight from SAN-LHR arrives), I should be able to drop that sector with minimal protest and instead terminate at LHR.
Thanks again - any thoughts / random speculation welcomed!