I think it might be cool if there was a way to track the loaded chunks, and keep those parts updated on the map. This might cause less lag than keeping the whole map loaded at all times, and will keep the relevant chunks updated more often.
Edit: While thinking about how the map is saved in server files, I realized that this idea doesn't make sense, but I'm keeping it up anyway in case the server saves the map in a different way than how I think it does, and makes this post relevant.
Once upon a time there were two pigs.
I gave them wheat, and they made a baby pigu.
Then, I got bored, so I killed them and ate their flesh.