I would have written my own entirely different protocol for an MMORPG. It was an idea for a tactical online RPG where everyone would take turns on a map (they had a limited time to decide what to do to prevent people from going AFK and the other team sitting there waiting forever for them).

It was all turn based and the only thing I wanted to download was data regarding where everyone was including any monster NPCs. True there is much going on, such as everyone, every battle instance, and all the locations in the world map, but my desktop could do it for thousands upon thousands of players, it's getting something that has the bandwidth to transfer all that data.

Knowing it would be hard to get anywhere near a good server, my turn-based system was great. The only thing being constantly transferred to the server was a little blip to let the server know a client is still alive.

Thinking of MMORPGs in general and the way they're designed, I wouldn't even touch the built-in 3DGS mutliplayer system since it's better for small sessions of players.