Does the lack of replies to this message mean that command line updating without Avast application running in systray is impossible?
If you mean the system tray icon not appearing (running), i.e., the ashdisp.exe process, it's totally possible.
If you mean a command line to start it (without the services running), it's only available in the Professional version (ashupd.exe).
The service aswUpdSv.exe does not to be running for manual updates (just the automatic ones).
The problem I see in trying to do this without avast running would be how it would check what is the current VPS and Program version to be able to know what incremental updates to download and updating current version after update.
The ashUpd.exe (from Pro version) check the files versions into the setup subdirectory of the avast folder installation.
Oh, like David said, respect the volunteer work of us