The only scenario when Danzo might win is 1, the rest Itachi obliterates him
How is danzo winning one? Itachi uses genjutsu which cannot be noticed and he loses . Shukaku said he can do that . Or speed blitz him . He lost to Sasuke's genjutsu . He aint winning one scenario at that level . Just no .
That's the scenario when Itachi just awakened mangekyou, on the other hand you have Danzo with less age and several Izanagi's chances (which I doubt Itachi even knew it's existence up to that point in time). At the very least it's worth discussing, the other 2 are not.
Danzo uses Koto and beats Itachi in all scenarios
Did you forget the entire purpose of Izanami? To strictly counter Izanagi the moment it's used. As has been stated to be done several times in the past forcing the ones that use Izanagi into a loop.
Danzo wins scenario 1 and 2 if Izanami and Koto Amatsukami is restricted. Scenario 2 since I doubt Itachi would be able to outlast Danzo's Izanagi. Although I'd say it's a big if since Itachi might not need to rely on MS and Danzo doesn't have a proper defense that would force Itachi to use MS.
Izanami takes prep time to set up the scenario and use, while Izanagi can be cast as is. I'm sure Danzo can get a couple of Izanagi's before Itachi can use Izanami (and that's assuming he even knows how to use Izanami at that time).
It took prep time when not being used against Izanagi. Which is why Itachi said its not exactly useful in combat. Why does it take prep time? He has to set up the loop. Izanagi does that for him by rewriting your death to try again. If it required the same prep against Izanagi than it would against someone not using it, then it wouldn't have been made to specifically counter Izanagi since it would be useless.
Actually, he says it's not exactly useful in combat because there is a way out of it, not due to prep time.
You must be registered for see images
I think otherwise, since it was explained that for Izanami to activate, the user had to remember their "body sensations" and then replicate the exact sensation again to actually activate Izanami.
You must be registered for see images
Now, let's take Danzo's usage of Izanagi as an example. He was alive, was shot dead by an arrow and then he appeared next to the arrow. For Izanami to actually work, Itachi would have to kill Danzo twice, using the exact same manner and then activate Izanami (or recreate the same scenario as with Kabuto). I don't think that by just activating Izanagi the user would be automatically be trapped in a pre casted Izanami, since the "body sensations" wouldn't be the same in both scenarios (meaning in one scenario danzo is shot with an arrow for example, and in the other he's just alive next to it).
And when they said that it was made to counter Izanagi, was due to the fact that Izanagi doesn't let you escape while trapped inside Izanami.