Why would the Italians want to serve on the EF?
Well Mussolini sent something like 10 divisions in OTL.
Personally I don't think the logistics exist for sending many more, atleast in the short term. Logistics is the field where all the problems with dramaticaly altering the situation of OTL exist. They certainly couldn't have hurled the entire Italian army to the east. An additional five or ten Italian divisions might have had an effect, but its pretty much impossible to say where they would have done so. In the grand scheme of things 5-10 divisions with subpar equipment is kind of neither here nor there.