Good idea, but can it really be justified on that type of car? I have a Quaife on my Alfa and it set me back 700GBP prior to fitting!!! Also unless you are driving the car hard (as in 100% throttle allot of the time) you wouldn't really be gaining much from the LSD other than traction from the line in the wet.
Something worth considering, the Alfa Romeo Q2 LSD was fitted to 147 and GT cars, some of which were the 1.9 16V Diesels. This differential is slightly different in application but also results in very similar performance to the Quaife units, and its less than half the price to buy!!! I would hazard a guess that it's likely to fit in a Fiat 5 speed box with some research into which Fiat/Alfa diesel gearboxes are cross over.
On the DMF front, these do wear because they have moving parts that allow each face of the flywheel to move a little in order to smooth out the engagement of drive (think tension springs in a turntable). Some use lubricant for the moving parts but this lubricant is not refreshed during the life of the part, so as this dries up the parts wear. These springs compress/decompress every time you lift the clutch when in gear and apply throttle. If you were to count how many times this action is repeated in a 2-4year driving cycle, you get an idea as to why they will fail. Add to that aggressive gear changes and heavy right foot and the lifespan will be reduced still.
There are some Fiat/Alfa parts/flywheels that are also cross-over that would allow a solid flywheel to be fitted, which are more robust but you would loose the refinement by doing so and are likely to end up with a more jerky pull from the car in the lower gears and from a standing start. For example the Alfa Romeo 155 16V Twinspark flywheel is a direct fit to the 1.9 JTDm 16V engines as used in the 147 and GT models. I know of a few cars that have been converted to solid flywheels in this way.
Humour