Would it be possible to make a world border that automatically shifts a few blocks every once in a while? (Also would it be possible to have the option to display the word boarder as a wall or line of red wool blocks, so that people in game know where it is without having to look at the map.)

Borders that move around by themselves are not planned, sorry.

I still have an idea for showing a pseudo-physical border of some sort (doesn't physically exist on server, but sent to clients as real), but my free time for the plugin is still limited and I have other ideas to work on for the plugin as well.