I'm not worried about neurotransmitter levels or electrical activity, there are enough events during a normal lifetime where these can be severely compromised without any long term effects. What I am worried about, though, is the fine structure of "custom" proteins - meaning proteins that have been specifically generated by the brain to modulate the activity of one or more very specific neurons. It's not unreasonable to suspect that these serve an important role in long term memory formation and function.

I strongly suspect digitizing the connectome by itself may not be enough in the same way that saving the structure of an artificial neural network without preserving info about any weights, activation functions, and other parameters is not enough to reproduce the network later.

> by copying the digital data to many archives and formats online and offline. No such option is available to a cryonics brain unless it abandons cryonics entirely

How you judge this depends on what you're trying to achieve with cryonics. In theory, a destructive scan of a cryo-preserved brain should yield more and better data than that of a plastinated one. The question becomes: do we need that additional data or not?

I'd like cryonics to preserve brains until it becomes clear how to scan them adequately. By comparison, cryonic preservation is a relatively gentle process, whereas plastination imposes some heavy chemical changes on the brain to the point where it's entirely likely that too much information could be lost. The promise of cryonics lies not in a biological resurrection at a later date, but in giving researchers enough time to figure out how to actually do an upload. It may well turn out that plastinated remains are a sufficient data source, but contrast that with cryonics where much fewer doubts about the preservation of the necessary information exist.

Of course, cryonics is beyond problematic - it requires constant and costly upkeep. And more importantly, just a few days of political, economical, or technological instability can easily wipe out every cryo-preserved brain in existence. So it's clear this can't be a solution for the next few hundreds or years. It's a solution for the next few decades at best (until the first provider goes bankrupt).

The options, in a word, all suck.