Your mandorla holds, but not because both circles are virtuous. A miner chasing only his own payout still has to earn it, because he fills his own block with other people's transactions. His subsidy is worth something only while the network those strangers use is worth something. Self-interest on that edge gets paid out as service to strangers.

It runs the other way too, and that is the strange part. Everyone's security is paid for by individually greedy miners, so nobody has to be good for the mechanism to work. The real risk to the almond is repricing. When the subsidy fades and fees have to carry the whole job, the overlap gets measured at a different width, and we will find out empirically where it lands.