Even your most powerful argument/worst-case scenario has immortality as its outcome

By "possible", I meant that we can imagine scenarios (however unlikely) where we will be immortal. Cryonics also relies on scenarios (admittedly not quite as unlikely) where we would at least have much longer lives, though not truly immortal. If being alive for a thousand years with serious brain damage still strikes you as much preferable to death, then I agree that my argument does not apply to you.

To what extent are we not "[serving] the ends of the elite" and "prevented from taking [our] own life if [we] found it miserable" even now?

In the US today, as a person of no particular import to the government, I feel I have considerable freedom to live as I want, and no one is going to stop me from killing myself if I choose. If on some construal I inevitably serve the elite today, I at least have a lot of freedom in how I do that. Revived people in a future world might be of enough interest that they could be supervised so carefully that personal choice would be severely limited and suicide would be impossible.