[wflynny]

What happens when one password is leaked somehow? Do you then have to reinitialize the matrix and reset all your passwords?

You also have the problem of some domains requiring alphanumeric only, etc., which then limits what characters you can use in all your passwords.

[theophrastus]

leaked password: choose a new/different two char index or path scheme.

alphanumeric only (some would say avoid such sites [shrug]): just continue along the path skipping over the non-alphanumerics until you've got the length you want.

[0xdeadbeefbabe]

Knowing one password is leaked somehow isn't an easy problem to solve. Why assume it is?