Why start with command line? That would imply some scripting or something. I'm lost on why you must use command line to connect. You will be using the mouse and keyboard once connected. Why not just use them to establish the connection in the first place?
If you use RAdmin Viewer to setup your connections you can define the properties of each connection and set it to start in scaled screen, full screen, whatever you want.
Basco Shower Enclosures
As someone who prefers to automate things I wholly agree that wanting to start via the command line is a reasonable request. For example using a shortcut to go directly to a session on a specific machine is handy either for speed of access of if you have a large phonebook.
And yes you can do that. There isn't quite the same degree of configuration as a phonebook entry but there's plenty to play with.
I'm not sure what the OP means by "scaled" (and it's an old post - not sure what version this post originally related to) but you can set the command-line switches for normal or for full screen.
If you read the Viewer help file you will see a full list of available switches.