What is special with your exchange model, as you say Next-generation exchange, Bitstamp has gold bullion's available for withdrawal from 2015-2016, so it isn't anything new???
How do you plan handle legal compliance as you are planning open digital bank? You need payment institution license, Coinbase acquired license not long ago
In cooperation with company Moro&Kunst Ltd. (whose representatives are part of Godbex team), Bitstamp was the first cryptocurrency exchange to offer the option of gold withdrawal, that was in late 2015. Godbex Exchange Module will not only enable gold purchase (withdrawal) but also a fast, cost efficient and easy position change between cryptocurrency and gold bars. Godbex exchange will introduce trading pair crypto/gold (one Troy ounce). Our partner Ceferin Law Firm is already preparing the necessary documentation for obtaining the digital bank license.