Regarding a neutral Italy that may or may not change sides, try this:
Minimum number of players: 3 - 1 player for AH/GE/OE, 1 player for RU/UK/FR/US, 1 player for Italy
Round 1: Italy stays Neutral. Italy may move army troops between territories but must stay within Italy and/or its colony. If attacked on R1, automatically join the other side.
Round 2: Italy decides between the powers. If Italy is not attacked before the beginning of its turn, then Italy must pick a side in the war. The Triple Entente and the Central Powers both may pass secret offers (written offers kept secret from the other side of the war). The two sides can promise whatever they want - military units, money, help conquering new territory - what ever you want. Both sides must have a secret, written plan for how they will fulfill their promises (e.g. Russia pays cash, France and England hand over units).
Units can be sent to Italy from other countries. Once the units sent to Italy arrive in a territory that started the game as Italian and that Italy still controls, the units is swapped for an Italian unit and remains under Italian control until destroyed.
The side that gets Italy has to keep Italy in order to win the war - what ever your side’s original winning condition is, add to it: “Must retain control of Rome in order to win.”
The side that loses Italy gets 1 new Inf raised in any European territory that borders Italy.
And that’s what I have to say about that.
-Midnight_Reaper