Note: You only need to crew Ghost Ark, which means you can use this effect the turn it comes down and dont need to risk it in combat
Timetwister is a powerful card, but probably not right for this deck, in that we want to accrue our own advantages, and give the opponent access to less outs to our threats (or to Armageddon)
While it is a decent removal option for creatures with mana value 3 or greater, there are more versatile removal spells like Fatal Push or Murder that can target any creature regardless of its mana value, making them potentially better choices depending on the deck's strategy
Sephiroth is a bit different, and getting a hold of his emblem is as easy as sacrificing a few creatures
Valley Rotcaller Decks like Chatterfang, Squirrel General look at Valley Rotcaller and see win condition. Any deck that pumps out a bunch of Squirrel tokens tends to be able to do so in bunches