In terms of a Post-War world in which the results are broadly similar, it seems crazy that the allies would intervene.
Fascist regimes, or regimes which were arguably similar enough were part of the allies, Greece and Brazil.
The US and UK may not like Mussolini's continued occupation of Ethiopia, but they're not going to go to war over it. The UK especially is in a terrible spot, Churchill is soon to be voted out, and either way the Soviet Union is clearly the bigger threat. Why entangle yourself with Italy for questionable benefits when Stalin could suddenly stream across the border. He probably won't, but clearly some viewed Anglo-American and Soviet conflict as inevitable. Italy, like Spain and Portugal is destined to be an ally in case of WWIII.
Of course, if it continues to occupy bits of Europe, like Albania, Yugoslavia, Greece, etc. that absolutely will cause problems.
At the same time, I think an Italy that invades Yugoslavia and/or Greece cannot realistically remain neutral. I'm imagining at most, it gets Yugo territories from Germany, but doesn't participate in conflict itself, or, perhaps more realistically, if we want a neutral Italy, Yugoslavia remains pro-Axis and Germany is firm it doesn't want to give Italy territory unless it joins the war, which it doesn't do. As a result, probably Bulgaria remains neutral as well, which is interesting.
If I were trying to write a neutral Italy scenario, getting rid of Mussolini would be well, a Godsend. If we could get Balbo in power he's not joining Germany. It wouldn't surprise me if Italy opportunistically jumps ship to nab Yugoslavia (if it remains pro-Axis, then probably joined by Bulgaria) and Austria to restore Austro-fascism.
Let's say the latter is the case, no adventurism in Europe, maybe Mussolini is still in charge, maybe not, Germany is defeated and partitioned broadly similarly to IOTL. To be simple, let's Italy doesn't jump in, or does so soo late it's perceived like Argentina and the war is basically done.
Italy won't be admitted to the UN initially, but eventually will.
The first post-war crisis is going to be fascinating, maybe the Arab Israeli War. IOTL, Italy ran a naval academy for Zionists, the original leadership of the Israeli Navy was trained in Fascist Italy. Still probably thinking the UK is a Mediterranean rival, Italy probably backs Israel full tilt, when IOTL only Czechoslovakia would sell Israel anything at huge markups, Italy may well be happy to donate significant amounts of kit and arm/train/send Jewish refugees from continental Europe to fight. This probably fuels further conflict with the British who in turn back the Arabs more strongly and send more support to Ethiopian rebels.
Long term, though, Britain will probably realize that if it wants to hold onto influence in its Empire, as will France, they need to be a united block with Italy and Portugal. Maybe they make up, maybe they don't.
Long term I think Italy's best bet is to gradually dominionize East Africa, and give Somalia and Eritrea big chunks of land from Ethiopia, and just not bother about Ethiopia proper and withdraw. Eritrea might, if sufficient Italians remain, end up as a constituent part of Italy. Since Eritrea and Ethiopia don't get along, and it was such a 'model colony,' it wouldn't surprise me if the Eritreans are actually generally okay with Italian indirect rule, as they may well prefer Rome to Adis Ababa. Somalia, if given tons of territory by Italy, might be less successful as a settler colony, but may well be somewhat content to remain a pro-Italian dominion for similar reasons, Rome is considered a better master than Adis Ababa.