I believe one thing that we should try to do here is making Anki more resilient to future changes in scheduling code.
If years later, we ever add additional parameters, upon syncing we will get this in the old client (or probably some other error):
Can we make it such that addition of extra parameters to the end is ignored by current FSRS? To be clear, I’m proposing future-proofing now so that we don’t need @expertium 's time machine (The Only 100% Foolproof Strategy Is Inventing A Time Machine) or need to do substantial changes in syncing.
Perhaps, there is a way?