Is there a way to hide arbitrary indicators (like messages, keyboard layout)?
I don't have enough screen resolution to have 10+ indicators, so I want to remove some that I don't feel are necessary.
To get rid of the messages panel you could just remove it. I did that too and it works fine:
sudo apt-get remove indicator-messages
I don't know how to hide the keyboard layout panel, but as far as I know if you remove all but one kayboard layout it will be automatically hidden.
Edit: So here is how to hide the keyboard layout panel: How to remove keyboard indicator?