Kenyth pretty much covered it. One thing to realize, even if a gaming company wanted to do that, there has to be a market for it. Most gamers don't have the predisposition to play a game like that.
To illustrate, Ultima Online (which, btw, allows you to do the kind of things you're interested in, except it doesn't use T$R rules) has a subscriber base of 240,000 - that's huge for _any_ game, but what really makes it lucrative is the constant stream of ten-dollar bills coming in every month. Most computer games sell less than 100,000. When you figure that a game company might get $30 per copy sold, it isn't hard to figure out that spending more than a million or so on a game is suicide.
(The above is one reason why so many companies want online games, they're
lucrative)
EDIT> Almost forgot! If you are interested in coding something yourself, you might want to look at
Exult, if you remember Ultima VII, exult is an opensource implementation of Ultima VII that allows you to use the data files in a store-bought copy of U7BG/U72SI to play on a "modern" os (eg, winblows, linux). It also has a studio tool to design your own adventures/maps.
[ 12-26-2002, 10:58 AM: Message edited by: Sir Krustin ]