Khers, let me first say, I really admire the idea and the effort you're putting into this project.
IT differ a little bit more.
Sort of. In a 60% layout (which seems to be the one discussed here), ISO-IT has five unique keys, while others are shared with other layouts. Please
check this link.
As for modifiers, ISO-IT is usually legendless aside for Tab which has legend and icon and Caps lock which bears the lock icon. Lastly the Enter key usually reads "Invio" as legend but it could be also be left with legend only like in the UK and the DE layouts.
In a more general view, I really believe this is an interesting idea, but not for a classic beige scheme; simply because localized classic beige sets do exist. I, for one, own a doubleshot and a dyesub OG ISO-IT set with those colors.
I would suggest to run this with a less popular but highly sought scheme, such as perhaps Skidata.
Skidata only exists in two ISO layouts, which are DE and NO, with the latter being extremely rare.
Localizing Skidata, maybe even including and ANSI Enter, would be successful in my opinion because also the inspired running GB has only keys for the standard ANSI layout.