You are right to call out the difference between "control" in the sense of keys and "control" in the sense of a network adversary. I should have been more caref

You are right to call out the difference between "control" in the sense of keys and "control" in the sense of a network adversary. I should have been more careful with my wording there. It is true that if 35% of the participating stake is suddenly prevented from contacting the network, no new blocks will be created. The word "participating" is important -- you can have stake that is not participating in the agreement protocol, but that is still spendable. The only way I can think of to mitigate the scenario you've described would be this: before going offline, you can broadcast a transaction which essentially removes your stake from the pool of participating coins until you're able to come online again. This would ensure the network can proceed without you.