Mixing Alfa with Dodge is not something a true "car guy" would do. Marchionne is a very smart and determined businessman, but he is an accountant, not a "car guy". That may put him at a slight disadvantage.
I know Alfa very well. I also understand the Dodge and Jeep brands. All three are very marketable products but I would never try to mix Alfa with Dodge OR with Dodge dealers.
Personally I don't have any plan for "Chrysler" as a car brand. A corporate name maybe, but not a car. A big luxury limousine is about the only thing that fits. A Chrysler Imperial. 'But how many could I sell? I would probably put this brand to sleep for a while.
Jeep is easy. SUV's AND small trucks. With new focussed non gimmicky styling its a no brainer.
Dodge is also an easy brand to position. All American cars and trucks. Muscle cars and a very tough image for trucks. Ad a few tough hybrids and diesels to improve gas mileage, but I would not build any very small Dodge cars. Dodge is not a good small car brand.
Small cars is a natural for the Fiat brand. The furtherest I would go with this Chrysler Fiat partnership is Dodge/Fiat dealerships and Jeep/Fiat dealerships.
I would definitely not put Alfa in that mix. Alfa is, or should be, a niche upscale young sporty brand with ZERO "Fiat-like" cars in its stable. If it can't stand on its own then I would start it off in the States with Maserati or Ferrari dealers. It should be positioned as the "very young man's Ferrari". Compete with the Asian "pony cars".