I have a fairly small screen and sometimes the text from chat almost completely covers my screen, I dont think Im the only person with this problem. I was wondering if you could either make the text smaller or have a command to change the text size.
You can do this already in the video settings of minecraft. Just change the GUI scale to small or whatever setting is best for you. Granted this will make your inventory screen smaller but this is what I did to minimize the amount of space chat takes up on my screen.
Playing in windowed-mode feels like it reduces how much the text covers the screen. I don't think you can make plugins to change chat like that. You might be able to find a client side mod, or HD texture pack that reduces the size of the text.