Few general tips:
-Extremely quick tempo
-Gargano to BWM support. He tries to win the ball higher up the pitch, and they actively press with the front three plus Gargano. (When and if Cavani feels like it

)
- The new match engine seems to understand 3-4-2-1 much better than in 2011, so I'd go with that as the basic shape. (Defensive wingers).
(-Given that the match engine would understand asymmetric front three properly though, I'd tinker with placing Lavezzi left to Cavani, and Hamsik alone in the hole, to Cavani's right. This might do-able with different roles as well- as in flat front three and Hamsik as a trequartista, Lavezzi as an AF with fair amount of creative freedom.)
- Against lone striker formations, one of the back three has an attacking role, usually Campagnaro. For the match engine to understand this, I'd switch to two man markers + a libero and drop the wide players to WB positions. I think you'd also have switch the front to 1-2, rather than 2-1, since I'm not sure how FM would interpret 2-1 with that shape. It could work though! Haven't tested it.
- Napoli tend to leave opposing deep-lying mids alone if they're not creative, and rather keep their shape and sit deep. The pressing starts when the ball crosses the half-way line, or even as late as their own defensive third.
I'll get back to this thread as soon as I've tried things out with Napoli, and try to be less vague.

Great topic, btw!