You are absolutely right in that sense. Mussolini is an opportunist, the sort of man who will take advantage of a situation if it tilts in his favour but not the sort of person to declare a massive, continent-spanning war "just because". In this Italy he will be even more of a mixed-reaction figure than in ours, since he will lack the Hitler association, plus, like I said, he will be responsible for certain territorial enlargments which will stick.
However, opportunism was what got Hitler into trouble. Sure, Mussolini can push the boat out a certain amount and get away with it, but one of the defining aspects of dictators is their tendency to gamble. Sometimes they win, sometimes they lose, but the more they win, the bigger they are willing to go on the next round. Mussolini started with Ethiopia, then moved on to Albania. It seems minimal when compared to Austria and the Sudetenland, but Mussolini wiped two countries off the map in the span of a few years, and he had not even moved on to his biggest claims. I do think that Mussolini, when left alone, can be just as much of a danger to himself as Hitler was.
Likewise, Italy is not the only one with plans to conquer and dominate Europe. Sure, Mussolini might make some mistake, or the French might stir things up, but it is also entirely possible that we see something like the Franco-Prussian War where Mussolini is tricked into starting something which he cannot control. As you said, he was cautious, but not a genius.
