I don't care about the satoshis, but I'd be way more interested if your arbitrage solution had cross-exchange transfers.
I read your terms and it said that I needed to have both balances on both exchanges for it to work : for example xxx BTC on
Exchange 1, and xxx USD on
Exchange 2, and if there's a
BTC > USD > BTC arbitrage path it'll use both balances..
Well, what's the point though?
Those 2 trades make 0 economical profit. In case there is a spread, it's going to be caused because of a value change between the two pairs, so if BTC is going down, then regardless of whatever arbitrage profit I just made, the whole value of my btc just went down, so I was better off selling everything to USD anyways. And vice versa.. The whole problem is keeping my money into two concurring currencies, if USD goes down BTC goes up. Why do I want to be making pennies if holding BTC makes me lose money every day.
I know you don't want withdrawal rights on your apis, which I wouldn't give to you anyways, but it's not impossible to implement other solutions :
1. Make the withdrawal / deposits manual by the user.
2. Have your own balance on every exchange, and instead of withdrawal / deposits that might take a few confirmations, cross-transfer between accounts.
3. I dunno, you're the business, think of something.
Either way good luck with your business, even though for trust factors I don't see myself using you a lot in the long run. Hope you don't disappoint your users!