Wespe, Grille, Hummel, Hetzer, Jagdpanther, MarderIII, Nashorn, PzIII, StuGIV, StuH. There are a lot of units to be used, but the main question remains: Can they create "Unique gameplay"? This is more important than the faction being German or Italian or anything else.
If they do the italians, it surely will be a different kind of fight, you can't rely on heavy tanks as OKW and Ostheer but you must rely on SPGs, the best examples are:
- Semovente 75/18
http://en.wikipedia.org/wiki/Semovente_75/18
- Semovente 105/25
http://en.wikipedia.org/wiki/Semovente_105/25 (for it there aren't many info in english)
The italian army will focus on the combination between infantry, artillery, light/medium tanks and SPGs.
PS: the other tanks you wrote should be given to Ostheer and OKW, especially for OKW i will give him the famous 88mm FlaK, the big guy that miss in CoH2. Anyway, i would take off Panzer III, for the ostheer i would send the Wespe, Hetzer, Jagdpanther and StuH42, for OKW Hummel, Marder III and Nashorn.