Don't upgrade to DSM7.0 then you will loose definitely Domoticz.
No USBSERIAL driver to connect your RFXcom will be updated so... stuck!
I migrate to Raspberry Pi1 and it works better than the Syno install.
since yesterday, I have this message which appears in domoticz. I clicked on the link to update it, but the update looks like it won't start This button has no function with domoticz on a Synology NAS. You will have to wait until @jumbotroll prepared a package (if at all possible for the ds115j ...