BitShares (BTS) is already supported by Bitsquare.
There is zero volume though, I think because most people in the Bitshares ecosystem do not yet realize they can easily go BTS->BTC->fiat from Bitsquare.
Or perhaps, we just do not like selling our BTS .... ;)
Adding SmartCoins support would be awesome though! Been meaning to write about that, but the post about adding SteemUSD did so badly that it hardly seems worth the effort.
Would you be interested in having BitUSD & co in Bitsquare?