We didn't discuss one thing which I think would be important for you. In order to effectively offer business and retail VoIP services I suggest to separate them and install one VoipSwitch server for RCs (retail) and one for PBX/UC. They can both access the same central database in order to keep your routing, suppliers, reporting, etc. consistent but the customers will actually use different SIP Server addresses.
For that I suggest to install in total 3 servers: Two VoipSwitch servers and one Database/RCS server.