Using other currencies that BTS has a base is good for outsiders. We at the community might be more interested in BTS but people from the outside who are just OpenLedger clients want to trade the main, usual pairs, which makes the base currency in this case OPEN.BTC.
For new users it's way better to have OPEN.BTC with other currencies other than BTS for the simple fact that not everyone is interested in BTS, we want everyone to use the exchange, not just BTS holders.
If we don't make it attractive to the outside we won't grow. It won't be the community alone making the exchange grow, ever. New users looking to trade the main currencies in a safe way, will.