I have billing on separate servers. Integrating would be relatively easy but pointless IMHO. If you are planning to saty very small then maybe but other than that you will outgrow a single server so you may as well start out with something scaleable.
Do I need to use the FusionPBX freeswitch/conf directory or the ASTPP freeswitch/conf directory? They are both quite different. Use differnet lua files, different SIP profiles etc. I copied all the lua files to the same location but there does not seem to be a way for both to be the default xml handler.