well, i have to see the events to give my opinion, but i can tell you this:
just put an event with:
a) Defend Italy!, Germany receives northern italy, and receives them as "core provinces".
b) Create RSI, RSI is created, germany receive military access to there.
the AI will always choose the first option, so if the player want to create the RSI, they have the option.
![Big Grin :D :D](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)
just put an event with:
a) Defend Italy!, Germany receives northern italy, and receives them as "core provinces".
b) Create RSI, RSI is created, germany receive military access to there.
the AI will always choose the first option, so if the player want to create the RSI, they have the option.