• First, we must define their assets. Instead of thirty X-wing fighters, they would have thirty runabouts or Peregrine fighters. Their base defenses would presumably consist of orbital defense platforms, although they would be insignificant compared to a Death Star.
• If they have capships at their disposal, they wouldn't fare any better than the defense platforms. Much like the Gungan theatre shield in TPM, the ANH Death Star shield was apparently semi-permeable, permitting passage only for slow-moving, small objects (this explains why the X-wings would accelerate to intercept the Death Star, decelerate to match speeds with it, and then "accelerate to attack speed" after passing slowly through the shield). Capital ships would never slip through its shield, thus making them useless (except as clay pidgeons for the Death Star's surface guns).
• Therefore, it would fall to the fighters to stop the Death Star, just as it did in the original battle. The fighters would have to lob a torpedo into the exhaust port in spite of the massive jamming which was described in the canon ANH novelization. This means they would have to get close enough to get a target lock and hope that their missiles fly true in spite of the jamming. It also means that they would have to make the trench run just like the X-wing fighters did, for the same reason (to fly in under the impenetrable defensive cross-fire over the port).
• This means they would have to fly largely on manual control, while evading TIE fighters and defensive blasts until they can get close enough to launch their missiles. Therein lies the first serious problem: Federation pilots are rarely capable of doing anything on manual control. Riker is considered an exceptional pilot (the best on the Enterprise, as we found out in "Chain of Command"), largely because he can do it while others can't.
• A second serious problem involves simple geometry. While an X-wing's proton torpedoes measure less than 0.5 metres in any dimension, a Federation photon torpedo measures 2.1 metres in length and 0.76 metres in width. This means that it is virtually impossible for a photon torpedo to approach the port from the side, make a hard 90 degree turn and enter the port without touching the walls, by virtue of its size. However, micro-torpedoes are smaller, so this problem would only apply to ships which have been outfitted with full-size torpedoes.
• A third serious problem involves maneuverability. While we witnessed Luke's torpedo execute a hard turn in ANH requiring many tens of thousands of g's of acceleration, we've never witnessed such maneuverability from a photon torpedo. Photorp turning circles are in the range of hundreds of metres or even several kilometres, not one or two metres. They've never demonstrated the ability to execute anything remotely like the ANH maneuver, which was a 90 degree turn inside a turning circle of one metre.
• If the Federation replaced the Rebellion they would be forced to adopt the Rebellion's tactics, which were the only way to attack the Death Star due to its shields, defensive weapons and jammers. But they aren't capable of duplicating Luke's shot into the exhaust port, due to problems with pilot skill and torpedo maneuverability.