You don't actually need an exchange as such....you just need an exchange mechanism that collects inputs of DRK or BTC and matches the two at an acceptable strike point.
Bob wants to sell 1 BTC
Jane wants to sell 1 DRK ( )
Both Bob and Jane send their coins to a holding address, effectively an escrow, and when there are two equally matched transactions, they are executed.
Probably not that far removed from what Master Nodes do now with their 8 rounds.
DRK Master Nodes as decentralised BTC exchanges....make it so.......
In a parallel world: Drk would be open source, AA would be singing its praises, KA confirms strong anonymity, a material chunk of the Btc community abandons Btc in favour of Drk, people forgive and forget the large mining at start and markets spring up around Drk that a copy cat clone can't replicate quickly enough.
That's the way to cement Drk's position in the community, so any challenger coins will find it tough to gain support. Instead, the people that missed out on Drk went and created their own scam anon coins. What a missed opportunity.