Load a different VMU in command line or in game?

I have run out of space on my VMU in demul. I can of course just back up the save file and create a new empty one. What I would prefer to to do is to load each game with a different VMU for each game.

Is it possible to launch demul through the command line and pass in the location of a memsave file to use for that game?

For that matter, is there a command line reference someone can link me to for demul? All I have been able to find is bits and pieces online.

Is it possible to swap memsave files in game with a hotkey?

Thank you!