Two main problems with Arb trading on BTC or any other alt-coin.
1) profit margins are very thin (~ 1% max) and BTC price movements cannot be hedged. Yes you can generate profitable trades with a 100 BTC worth of trades but if the BTC price declines by 15% during that time period your profits are more than offset
2) lack of viable hedging tools to lock in prices and do real arb trading
1-Yes but sometimes you will profit if the price goes up or declines 15% depending on if you are in cash or bitcoins at the time.
2-You can create your system.