What I would I like would like to see is an option for Emacs Latin postfix input method.
Ivan Avery Frey

Does a normal italian layout have keys that should behave like this?. I mean, is this how it works on Windows or OSX, or is it a Emacs specific thing?

Also, which keys are used for this? from what I can see you have specific keys for accented letters. Which key does Emacs use for accents?

Italian layout

What accents are used for italian?, my guess would be _̀ and _́ but I only see a key for the first one.

Depending on how do you expect things to work, there may or may not be a way to get this working easily. I will tell you if I find something out.