There's a system not too far removed from what you're talking about;
www.doxygen.nl/
But - this is relatively important - this is just as much work. You will not be doing any less work just because the text is somewhere else. Also, you'll still need to extract and parse the docs for use internally. Also, you'll need to stick to a common format for the mud user to actually be able to use the output.
I'm not sure you'll save much time, compared to just updating help.hlp.