The 25 BTC are reserved as input for the DAO genesis. See bisq-docs/dao/phase-zero.adoc at master · bisq-network/bisq-docs · GitHub
Adding another base currency is laid out here:
But note that from the 3 other base currency one (DOGE) had zero activity and LTC and DASH has also super low activity. So why should it be more successful with any of those you mentioned?