As a Roblox developer, it is currently impossible to automatically publish my changes to a Roblox place via command line or plugin.
If Roblox is able to address this issue, it would improve my development experience because I would be able to publish my game automatically after performing a plugin action, for example synchronizing game contents externally with Rojo or Lync.
Rojo currently uses a second party serializing program to generate an RBXL file which gets uploaded to Roblox using the Place Publishing API.
Lync is currently in development as a replacement for Rojo with the same goals and features in mind. If StudioPublishService:PublishAs(…) is not exposed to PluginSecurity, it too will need to use a serializing program.