[plamzi]

I think what you're asking for would be a very hard sell, even in the non-commercial world of MUDs.

As I think KaVir mentioned before, vertical development is used to give everyone, even unsophisticated thinkers, a clear sense that they're progressing. But vertical development is no more than a 'ticker', a numeric measure of how much time you've invested.

In the meantime, what you call horizontal development is always the only real development taking place--i. e. learning how to interact with the world more effectively, how to lead and play in a team, how to contribute to the game, etc.

By comparison to pretty much any other type of game, MUDs already have a super-wide horizontal development axis. Most of them can easily keep you learning for a decade. But what you seem to be asking for is a diminished vertical axis (to match your sharp sense of realism) and an even broader horizontal one (two decades, maybe three?).

In short, I think the closest game to what you're looking for is called 'life'.