Crypto Trading: USD as a Base Currency

I have accounts in Bittrex but I think it's difficult to calculate real return due to the price volatility of BTC itself. I tried bitstamp as well but it has very limited currency pairs so it's worthless

It seems their is a gap currently with none of exchanges offering USD as the base against a basket of Cypto currencies and alt coins. If you know about such platform, please post in the comments, will really appreciate your feedback.