It's also not impossible to trade via bitstamp and bitthumb, sure it may take an hour or so to get your btc from bitstamp to bitthumb but that's not the bottleneck. Once you sell on bitthumb for USD you need to get that USD back to bitstamp. So you have to get it from a Korean Bank to your own account and then to bitstamps European bank account. Best case scenario that route takes 5-10 working days so the BTC network taking an hour or so to confirm is the least if your problems.