Shoutbox

I suppose someone could write a script to compress the message on this end (using an algorithm or so), and inflate it on the other, but you'd both need the script for that.

AFAIK apart from this, there's no way around the SendMessage limit. This is due to the maximum size of a message packet being dropped if the whole thing is bigger than 1664 bytes - maybe someone had been drinking Kronenbourg or something.