I don’t believe addm supports installing os updates outside of any product updates provided by bmc.
You can do updates via a command-line I believe...
So yes, it's possible. However installing an RSCD Agent on the appliance is not supported, although it "may" work because the appliance is basically RHEL 6 with tideway on top... If you can't install the agent though, you could use ssh to call the command from BSA.