I believe Izanami to be a technique which effects are similar to it's counter part Izanagi but at the same contrary in it's application(I hope that makes sense )...
In other words if Izanagi allowed the user to bend his own state of existence to the point of avoiding death,my guess is that Izanagi would not bend reality and make it illusion like Izanagi but rather bend imagination and make it reality
But it's not a stretch to say it could actually turn out like that.If you come to think of it Banbutzu Sozo was the technique the sage used to shape things with his imagination and give them life,and the Uchia's are the clan who inherited the power of the eyes of the Sage,but I guess they're variant would be limited only to the shaping things with imagination and not giving them the lifeforce as they lack it(because it belongs to the younger son's heritage)[/I]
Honestly that would make sense as Itachi himself stated it's a jutsu that goes in partnership with Izanagi
That's just my 2 cents