S4Group is in process with several devices. Look in pro forum or search for it think it's S4group.
The FX-60 which comes with N2 by default and add a 2 port rs-485 card and BACnetMSTP drives will support 150 devices. If you are looking to "Convert" the N2 straight to BACnet so you can connect to XYZ brand network manager then the FX is overkill cause you will likely spend twice the laobor in programming. Fiels server may have what your looking for.
If sense were so common everyone would have it !
All opinions expressed are my own. Any advice provided is based on personal experience, generally accepted fact or publicly available information. As such, it is worth exactly what you paid for it, not a penny more not a penny less !!