I'll start out by saying I LOVE the firespray. It's been my favorite ship in the game for quite some time now.
That being said, it's clearly the least used large ship in the game currently. For evidence go to the regionals thread. Imperial firesprays are basically non existent, and the scum firesprays don't seem to get much play outside of boba (mainly to get him at PS 10).
So why is this? It's not a bad ship by any means, my success with using them can attest to that. They do suffer a bit from the "x-wing syndrome" in that they are good at a lot of things but not really great at anything.
They don't have a 360 turret, can't barrel roll or boost, only have 1 crew slot, no systems slot, and have 2 agility which is often the worst agility value to have.
So what's needed to "fix" them, or at least give them more play? More pilots wouldn't hurt, but I don't think that's the answer necessarily. They could definitely use a better title, they have 2 and both are mediocre at best. They have plenty of good offensive options so that's probably fine as is, but they could use help on defense.
Personally I'd like a Tie/D type fix. A small cost reduction when not using any of your secondary weapon slots, as well as a possible free evade for certain maneuvers.
A couple other ideas would be adding a crew slot for every secondary weapon slot not in use, or a title that gives you the system slot.
Any other ideas?

