Betbtc was a BTC bet exchange for 4,5 YEARS!.. They had everything, Betfair interface, good odds and API.. it had shit liquidity and in the end became (had to become) a sportsbook..
It's very hard to drag people away from Betfair. They have a monopoly and whoever tried to challenge them in the past, has failed. I still remember back in the days, when they introduced the premium charge and everyone was raging. In the Betfair forums there was a call to leave Betfair and play/trade at Betdaq instead. The traders agreed on meeting in certain markets and do their business there. This worked a bit, but the liquidity was still way below Betfair. And of course you don't want to trade with/against fellow pros, but you want lots of noobs in the market. And these noobs didn't bother to move to Betdaq, because Betfair was still very liquid and these noobs were not affected by the premium charge. So everyone went back to Betfair and Betdaq remained just another exchange with no volume until today.
This is all fascinating to witness. I guess all other betting exchanges have better conditions, better customer support, aren't that greedy etc., but still everyone stays at Betfair or some white label solution of them. I don't think this will change in the foreseeable future, but one can try

With lots of patience.....and money.