I am unsure of how I feel about the Flechette Cannon, it could be very strong in the right build. Right now I think you are giving up an awful lot to dish out a stress, and there are already a lot of ways to do that without the sacrifice of damage. If a ship already has a stress this card gets a lot less attractive. At 2 points you can do worse, but I think there are better options for both the Cannon slot and for dealing stress.
The Mangler looks solid, and as has already been stated, looks to be an obvious choice for a thrifty Outrider.
The M3-A Interceptor is neat, and it is certainly affordable, but at 18 points it is competing with the excellent Z-95 choices for a slot in S&V lists. This looks to be a similar competition to what the Rebels have with A-Wings and Z's. The A-Wings have fit into a completely different role, and I think that S&V brings a lot to the table to make the Z-95 more attractive, such as the Illicit Upgrade availability on the base Z-95. I am hoping that we see some of the other pilots soon.