This is exactly what market makers do. During violent moves prices vary wildly between exchanges and market makers become takers. They instantly buy and sell the same amounts on different exchanges without risk, then re-balance their accounts.
No. To buy and sell on your own schedule, you must take liquidity, paying the spread. This is not what market makers do, they sell liquidity. And it becomes less possible to find efficient clearing trades during rapid moves, because the spread widens exactly because market makers don't want others to arbitrage them.
