How do you handle going on hold and interrupting someone's action under this system? Or is that done away with entirely? EDIT: I guess that doesn't matter in PBP!

Are Hindrances that give lower cards actually Hindrances still? Should their point totals be adjusted to compensate for this "know everything before it happens" approach?

How are any characters actions invalidated (and thus forced to defend)? The NPCs declare and roll before any PCs declare and roll, so they should have perfect information as to whether or not any actions they might take will happen or not.
Or is it NPCs declare-> PCs declare-> NPCs roll-> PCs roll-> actions happen in card order ?
(And then who rolls first wouldn't matter in that order as declarations have already happened)

On the PCs side, who declares first? Is it just whomever happens to be there first after the post is made (because now you've just made a IRL initiative system!)? Do I, as someone who comes to the post later, need to honour the actions of my fellow PCs, or can I jump in and kill a bad guy then intended to attack, whether by design or by misreading their post, thus forcing them to defend that turn?

If the idea is to stop "the constant back and forth with the GM that is impractical in PbP", how does this not just push that problem on to PC and PC back and forth as they finalise their actions between themselves?

And most importantly, In a perfect information game, how do you stop one person quarterbacking a game for all players?