Missile Boat would be OP'd given that it was designed around 1 objective, take out the Tie Defender.
Star Wing would be a great add for an Imperial splinter that needed some extra oomph, since they're faster (although still slow) and shielded and thus have a HUGE advantage in survivabity when compared to the Tie/Sa, while not being any heavier armed, being able to survive to make more than 1 pass (probably) makes them far superior.
And they had ion canons. Basically they’d be better than a Y-wing but worse than a Skipray, closer to the Y-wing