Italy was even before the start of the war a great power and her remaining neutral will mean that ITTL WW2 will be totally different from ours; on the same note, no, Italy will not be snubbed in the new world order, she is too big to be ignored (and untouched by all the destruction) and this will also create a total different decolonization process.
Nobody says Italy will be snubbed forever. It will certainly be snubbed in 1945. Eventually, though, just as Spain joined in the UN, so will Italy.
Note, BTW, that another neutral, Sweden, managed to join as early as 1946. But the problem is that some seem to see the UN as a monolith. In 1945 it actually already is the lowest common denominator of mutual vetoes. Sweden happens to fall within it. Italy won't.
Consider:
- Italy is ruled by the Fascists, thus anti-Communist - a big thumbs-down from the Soviet Union;
- Italy is ruled by the Fascists, thus non-democratic - something of a thumbs-down from the USA;
- Italy has (and we go back to the thread topic) colonies - lots of new countries dislike it.
Add that the French, in particular, and de Gaulle, in particular's particular, will loathe seeing Italy get a chair at the table for free.
This also brings us to the Italian behavior as a neutral. By the late war, Sweden had managed to gracefully become a pro-Allies neutral. Had it continued to behave as it did in 1941, I doubt they would have gotten in by 1946.
So how has Italy behaved, as a neutral?
Now, on to the colonies:
AOI: while it will be a guerrillas hotbed, in the early 40's the abyssinian will not receive any help from the Wallies, unlike OTL, as it will be more important keep Rome friendly
Hmmm. So maybe they receive help from the Soviets in the early 50s. That in turn means help for the Italians by the USA, probably.
Lybia: going for an italian majority, at least in the city.
Possible. You are aware, naturally, that the Falklands, with a 100% English-speaking population that self-defines as British and regularly votes for remaining British, still is on the UN list of non-self-governing territories.
Albania: will be difficult for the Albanian to shake off italian control, too little distance between the two and Benny send colonist even there
In the short run, yes. And in the long run, if Italy joins the NATO/OTAN and Albania has strategic value. On the economic side of things, and after Mussolini retires/dies, the Italians might also write Albania off as a money drain.
Neutrality: sure Rome will remain neutral, this doesn't mean that she will do it for free or/and will not try to get the best from this situation, attempting to get concession from Greece and Jugoslavia and later to retake control of Austria
Greece joined the NATO/OTAN in 1952, before Western Germany. Italy will keep the Dodecanese, and that will be it. As to the rest, you seem to be thinking in 1930s terms. Austria would be spoilt for a choice for powerful supporters (two sides to pick from) in case another neutral harasses them even just a little.